Evasion of human innate and acquired immunity by a bacterial homolog of CD11b that inhibits opsonophagocytosis

Microbial pathogens must evade the human immune system to survive, disseminate and cause disease. By proteome analysis of the bacterium Group A Streptococcus (GAS), we identified a secreted protein with homology to the alpha-subunit of Mac-1, a leukocyte beta2 integrin required for innate immunity to invading microbes. The GAS Mac-1-like protein (Mac) was secreted by most pathogenic strains, produced in log-phase and controlled by the covR-covS two-component gene regulatory system, which also regulates transcription of other GAS virulence factors. Patients with GAS infection had titers of antibody specific to Mac that correlated with the course of disease, demonstrating that Mac was produced in vivo. Mac bound to CD16 (FcgammaRIIIB) on the surface of human polymorphonuclear leukocytes and inhibited opsonophagocytosis and production of reactive oxygen species, which resulted in significantly decreased pathogen killing. Thus, by mimicking a host-cell receptor required for an innate immune response, the GAS Mac protein inhibits professional phagocyte function by a novel strategy that enhances pathogen survival, establishment of infection and dissemination.

Mechanisms of exacerbations

Exacerbations of chronic obstructive pulmonary disease (COPD) are a major cause of morbidity and mortality and hospital admission. Some patients are particularly susceptible to develop frequent exacerbations; exacerbation frequency being an important determinant of health related quality of life. Patients with frequent exacerbations (three or more exacerbations per year) have increased induced sputum cytokine interleukin (IL)-6 and IL-8 levels when stable, suggesting that frequent exacerbation is associated with increased airway inflammatory changes. Respiratory viral infections are a major cause of COPD exacerbations, with upper respiratory tract infections (colds) being associated with two-thirds of COPD exacerbations. Rhinovirus has been detected in induced sputum by PCR in 25% of exacerbations, suggesting that rhinovirus may directly infect the lower airway triggering exacerbation. The presence of an upper respiratory tract infection leads to a longer symptom recovery time at exacerbation. At exacerbation induced sputum IL-6 levels were increased compared to stable, though there were no significant increases in IL-8 or sputum cell counts. Sputum IL-6 levels were found to be higher in those patients with symptoms of a common cold. Increased airway eosinophilia has been also found at exacerbation. Other factors including bacterial colonization of the airways, temperature and interactions with environmental pollutants may also play a role in COPD exacerbation.

[Using amyzon in the treatment of patients with sore throat]

Presented in the paper is experience gained with the use of a new Ukrainian drug amyzon in treating angina. Administration of amyzon in adult patients with angina was noted to make for a quicker eradication of the infectious toxicosis syndrome and manifestations of local inflammation, normalization of the peripheral blood picture and indices for immunologic homeostasis. With amyzon complications develop less frequently. Angina patients when placed on amyzon tend to run a shorter course of their illness and achieve long-term clinical remission, which fact permits recommending its use in a complex therapy of angina in adult patients.

Antibodies to streptococcal surface enolase react with human alpha-enolase: implications in poststreptococcal sequelae

The pathogenic mechanisms for developing acute rheumatic fever after group A streptococcal pharyngitis are still poorly understood. The glycolytic enzyme enolase is one of the major proteins on the surface of group A streptococci. Herein, significant cross-reactivity was shown between streptococcal enolase and human enolase. Fluorocytometric analysis revealed that antistreptococcal enolase antibodies react with the enolase expressed on the surface of hematopoietic cells. Furthermore, the enolase on the leukocyte surface was found to be up-regulated by inflammatory stimuli. Evaluation of antibody titers indicated that serum samples from patients with acute rheumatic fever have higher levels of antibodies that react with the human and bacterial enolases than do serum samples from patients with streptococcal pharyngitis or healthy control subjects. These results show that streptococcal enolase is a novel cross-reactive antigen that may play an important role in the initiation of the autoimmune diseases related to streptococcal infection.

[Humoral immunodeficiencies in asthmatic children with recurrence rhinopharyngitis]

OBJECTIVE

To determine the serum immunoglobulin concentrations in children with asthma and recurrent rinofaringitis.

MATERIAL AND METHODS

We made a descriptive survey in children with persistent moderate asthma and with recurrent infections. Serum IgA, IgG, IgM and IgE concentrations was determined in the laboratory of Immunology and the results were considered according to the age and to the technique used in the laboratory.

RESULTS

They were 45 patients (26 males and 19 females) with age average of 5.5 +/- 2.8 years +/- SD. In 12 patients (26%) had deficiency of IgA, in 2 (4%) it was absolute and in 10 (22%) it was partially. They were 4 (9%) with deficiency of IgG and IgM had not deficiency, but in 5 (11%) had elevated concentrations. We find 28 patients (62%) with high serum IgE.

CONCLUSIONS

The prevalence of the serum immunodeficiency would be bigger if they were looked for deliberately in groups with risk, like it is demonstrated in this study, where, of the 45 patients they met 18 with some serum immunoglobulin deficiency (40%).

Pharyngeal carriage of group C and group G streptococci and acute rheumatic fever in an Aboriginal population

Acute rheumatic fever (ARF) and rheumatic heart disease (RHD) represent an autoimmune response to group A streptococcal pharyngitis. In the Aboriginal population of the Northern Territory of Australia, some of the highest rates of ARF in the world have been reported, although throat carriage rates of group A streptococcus in this population are extremely low and symptomatic group A streptococcal pharyngitis is uncommon; by contrast, carriage rates of group C and G streptococci are high. Therefore, we questioned the involvement of these groups in ARF and showed that they have the potential to elicit an autoimmune response that may trigger ARF.

[Cellular content of mixed saliva sediment in patients with chronic mucosal inflammation]

A comparative analysis was made of the saliva sediment cell composition in healthy patients and patients with chronic mucosal inflammation. Migration of leucocytes to the oral cavity was registered in patients with chronic inflammatory processes. A reliable increase in the number of epithelial cells with high degree of destruction was determined in saliva in addition to the appearance of cubic epithelial cells. These results indicate certain violation of epithelial reparation. It is proposed to use a quantitative analysis of saliva sediment for estimating functional conditions of mucosa.

Bacterial determinants of persistent throat colonization and the associated immune response in a primate model of human group A streptococcal pharyngeal infection

Group A streptococcal (GAS) pharyngitis and the subsequent bacterial colonization of the human throat elicit an immune response that may precipitate acute rheumatic fever in a susceptible host. To study the bacterial determinants that influence throat colonization and induction of humoral immunity, we characterized the behavior of GAS strains in a baboon model. An M-type 3 clinical isolate of GAS typical of strains that cause pharyngitis and invasive infection was recovered from the pharynx of six out of six baboons for at least 6 weeks after oral inoculation. By contrast, an isogenic mutant deficient in M protein failed to colonize most animals or was rapidly cleared. An isogenic mutant deficient in hyaluronic acid capsule colonized five out of six animals, but only persisted in the pharynx for 14-21 days. Colonized animals developed serum antistreptolysin O (SLO) and anti-M protein immunoglobulin (Ig)G. The kinetics of the antibody responses were similar to those seen after human infection. Peak titres increased with the duration of throat carriage. Colonization with GAS prevented recurrent colonization after challenge with the homologous wild-type strain, but not after challenge with a strain of different M protein type. Early clearance of the M protein-deficient strain was associated with increased susceptibility of this strain to phagocytic killing in non-immune serum, whereas clearance of the acapsular strain was associated with increased susceptibility to phagocytic killing in the presence of specific antibody. These studies support critical and distinct effects of the GAS M protein and capsule on throat colonization and induction of humoral immunity in a model that reproduces important features of pharyngeal colonization and immune response following human infection.

Management of group A streptococcus pharyngitis with a second-generation rapid strep screen: Strep A OIA

Empirical therapy of presumed group A streptococcus (GAS) pharyngitis leads to unnecessary and inappropriate use of antibiotics and pressure for emergence of resistant strains of common bacteria. Immunoassay technology has produced several rapid tests for GAS. The wide variations in diagnosis and treatment of acute pharyngitis are reviewed including the impact of rapid strep tests. Published studies comparing Strep A OIA to routine agar culture and other rapid strep screens are presented to assess the reliability and applicability of this novel assay. These data suggest that Strep A OIA may be superior to the "gold standard" throat culture and other rapid streptococcal antigen detection assays. Judicious use of Strep A OIA can result in rapid, precise diagnoses and eliminate unnecessary and inappropriate use of antibiotics. Careful antibiotic selection can reduce the pressure for emergence of resistant bacteria. This innovative, effective assay can contribute to a lessening of this serious clinical challenge.

[Immunologic correctors in combined treatment of paratonsillitis]

As shown by immunological examination of 47 healthy subjects living in polluted territories and 120 patients with paratonsillitis (PT), PT arises in T-cell and humoral immunodeficiency of the palatine tonsils. Conventional treatment fails to eliminate initial immunodeficiency, contributes to development of chronic inflammation and complications. Adjuvant treatment with local polyvalent pyobacteriophage and parenteral placental albumin improves local and systemic immunity, promotes a favourable outcome of acute inflammation in the tonsils.

Clinical and biological characteristics of immunopathological disease-related erythema nodosum in children

We report a series of 22 children with idiopathic, drug unrelated erythema nodosum (EN) admitted to our Department. In 5 of them an history of streptococcal pharyngitis was referred; the remaining patients came to us with a diagnosis of "EN of unknown origin". Acute phase reactants, immunoglobulins, stool alpha1 antitrypsin, ANA, anti dsDNA antibodies and ANCA assay, chest roentgenogram, tuberculin test, and ophthalmologic assessment were performed in all patients. Etiologic diagnosis was made in 16 patients: Streptococcal pharyngitis (5 cases), chronic inflammatory bowel disease, IBD (3 cases), Behçet syndrome (2 cases), Yersinia enteritis (2 cases), infectious mononucleosis, atypical mycobacterial infection, immunodeficiency related infection, and SLE-like syndrome due to C4 deficiency (1 case each). We found oral/scrotal aphthae in 3 cases, gastrointestinal symptoms in 5 cases, arthritis in 3 cases. Acute phase reactants were positive in 16 patients without correlation to the underlying disease. Conversely, the increased alpha1 antitrypsin stool excretion and IgA serum concentration seemed to represent helpful indicators of IBD and Behçet syndrome, respectively. Proinflammatory cytokine pattern showed increased IL6 serum concentrations both in infectious and in non infectious disease-related EN, whereas a minor involvement of TNF was found in these patients.

[Diagnostic value of rapid streptococcal antigen test provided by Abbott "test pack strep A": current report]

The upper respiratory tract infections are the most frequent infectious diseases in human. Beta haemolytic streptococcus group A is the most common etiologic factor of bacterial pharyngitis. Delayed or inadequate treatment of streptococcal pharyngitis can cause serious subsequent complications. Only a part of patients show typical features of the disease so that the diagnosis can be based on clinical appearance alone. For this reason we propose direct antigen test as a rapid useful method which allows detection of group A streptococci in throat swabs. The aim of the study is to estimate clinical value of rapid antigen test in differential diagnosis of pharyngitis in children and adults. We have performed 50 tests using commercial kit--Abbott Test Pack Strep A. Simultaneously conventional bacterial throat cultures were performed. The comparison of results acquired by both methods did not revealed any differences.

Immunological relationship between the class I epitope of streptococcal M protein and myosin

The class I epitope of streptococcal M protein is an epidemiological marker for acute rheumatic fever (ARF)-associated serotypes of group A streptococci and is recognized by anti-M protein monoclonal antibody (MAb) 10B6. Using MAb 10B6, we determined the relationship between the class I epitope of M protein and the alpha-helical coiled-coil protein myosin. MAb 10B6 reacted by enzyme-linked immunosorbent assay and Western blotting with human cardiac myosin and rabbit skeletal myosin and its heavy meromyosin (HMM) subfragment. Overlapping synthetic peptides of M5 protein were used to identify the region of M5 protein recognized by MAb 10B6. Two C repeat peptides (C2A and C3) containing the amino acid sequence KGLRRDLDASREAK reacted with MAb 10B6. Partial sequence identity, RRDL, was found in the HMM fragment of myosin, which reacted with MAb 10B6. However, not all peptides of M5 protein and myosin containing the RRDL sequence reacted with MAb 10B6. ARF sera and sera from uncomplicated pharyngitis (UNC) reacted with C repeat region peptides of M protein, while acute glomerulonephritis sera were not as reactive. Affinity-purified human antibody to peptide C3 reacted with myosin. The data demonstrate that the class I epitope of M protein is immunologically cross-reactive with myosin and the HMM subfragment, and antibodies to peptide C3 and myosin were present in ARF and UNC sera.

Acute pharyngotonsillitis is an infection restricted to the crypt and surface secretion

A commonly accepted hypothesis is that acute pharyngotonsillitis is caused by bacteria which first adhere to the epithelial surface and then invade the tonsillar parenchyma; however, evidence directly supporting this hypothesis is not available. In previous studies on acute pharyngotonsillitis, we found that the secretion in crypts and at the surface was infected in acute pharyngotonsillitis while no bacteria were detected in the parenchyma. Based on these results, we have proposed a new hypothesis stating that the infection is restricted to the crypt and surface secretions in acute pharyngotonsillitis. To evaluate this hypothesis further, in the present study we examined tonsillar tissue and secretion from patients with acute pharyngotonsillitis, recurrent pharyngotonsillitis and healthy tonsils. Surface secretion was studied after sampling by an imprint technique followed by routine histological preparation. Tonsillar tissue was examined by fluorescence microscopy after staining with acridine orange and by transmission electron microscopy. There were high numbers of bacteria and moderate or extensive ongoing phagocytosis in the crypt and surface secretion from patients with acute pharyngotonsillitis. Bacteria, leucocytes and phagocytosis were also present, but to less extent in the secretion from patients with recurrent pharyngotonsillitis and to even less extent in the healthy controls. In none of all the investigated tonsils were bacteria present in the parenchyma. Bacterial adherence to the epithelial surface was only very rarely observed. This study supports the hypothesis that acute pharyngotonsillitis is an infection restricted to the crypt and surface secretion and that bacterial adherence is not of significant importance in the pathogenesis of acute pharyngotonsillitis.

Pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections: clinical description of the first 50 cases

OBJECTIVE

The purpose of this study was to describe the clinical characteristics of a novel group of patients with obsessive-compulsive disorder (OCD) and tic disorders, designated as pediatric autoimmune neuropsychiatric disorders associated with streptococcal (group A beta-hemolytic streptococcal [GABHS]) infections (PANDAS).

METHOD

The authors conducted a systematic clinical evaluation of 50 children who met all of the following five working diagnostic criteria: presence of OCD and/or a tic disorder, prepubertal symptom onset, episodic course of symptom severity, association with GABHS infections, and association with neurological abnormalities.

RESULTS

The children's symptom onset was acute and dramatic, typically triggered by GABHS infections at a very early age (mean = 6.3 years, SD = 2.7, for tics; mean = 7.4 years, SD = 2.7, for OCD). The PANDAS clinical course was characterized by a relapsing-remitting symptom pattern with significant psychiatric comorbidity accompanying the exacerbations; emotional lability, separation anxiety, nighttime fears and bedtime rituals, cognitive deficits, oppositional behaviors, and motoric hyperactivity were particularly common. Symptom onset was triggered by GABHS infection for 22 (44%) of the children and by pharyngitis (no throat culture obtained) for 14 others (28%). Among the 50 children; there were 144 separate episodes of symptom exacerbation; 45 (31%) were associated with documented GABHS infection, 60 (42%) with symptoms of pharyngitis or upper respiratory infection (no throat culture obtained), and six (4%) with GABHS exposure.

CONCLUSIONS

The working diagnostic criteria appear to accurately characterize a homogeneous patient group in which symptom exacerbations are triggered by GABHS infections. The identification of such a subgroup will allow for testing of models of pathogenesis, as well as the development of novel treatment and prevention strategies.

Temporary suppression of cell-mediated immunity in standardbred horses with decreased athletic capacity

Eighty Standardbred horses, originating from 5 training campuses, with decreased athletic performance in association with symptoms such as intermittent fever and mild pharyngitis were examined. As control animals, 10 horses from a stable with normally performing horses were used. Virus isolation and clinico-chemical and serological tests were performed. Lymphocyte proliferation tests were carried out to evaluate the capacity of the cell-mediated immunity. In addition, a bioassay for equine type I interferon, as a marker for early viral infections, was established. No specific microbe could be linked to these symptoms, but there was a temporary suppression of the cell-mediated immunity, which might be explained by the serological evidence of an EHV-2 and/or rhinovirus infection.

The effect of a rapid kit for detection of streptococcal pharyngitis on the accuracy of the physicians' diagnoses

BACKGROUND

In the last decade, the accuracy of rapid tests for detection of group A streptococcal antigen was evaluated in laboratory and clinical settings, and the tests were suggested as an alternative to the traditional throat culture.

METHODS

We evaluated 19 patients with a preliminary diagnosis of nonstreptococcal pharyngitis and 13 patients with a preliminary diagnosis of streptococcal pharyngitis. The physician performed a rapid latex agglutination test (Detect A Strep), took throat culture from all of the patients, reconsidered the preliminary diagnosis, and made a working diagnosis. A clinical score was calculated for each patient during data analysis. The accuracy of the physicians' preliminary diagnoses was compared with the accuracy of the scoring system, with the accuracy of the latex agglutination test, and with the accuracy of the physicians' working diagnoses.

RESULTS

The scoring system, the physicians' preliminary diagnoses, the latex agglutination test, and the physicians' working diagnoses correlated significantly with throat culture results (p < or = 0.05). The efficiency of the physicians' preliminary diagnoses was 75% compared with an efficiency of 69% of the clinical scoring system, an efficiency of 66% of the latex agglutination test, and an efficiency of 69% of the physicians' working diagnoses. The physician changed the preliminary diagnosis only for two patients as a result of the latex agglutination test results; ironically, however, the preliminary diagnosis was correct in both of these cases.

CONCLUSION

The use of a rapid test for the diagnosis of group A streptococcal antigen under normal working conditions did not improve the accuracy of the physician's diagnosis, so the use of the latex agglutination test in this study was not cost-effective.

Immunoglobulins inhibit adherence and internalization of Streptococcus pyogenes to human pharyngeal cells

Purified human sIgA against group A streptococci inhibited streptococcal adherence to pharyngeal cells whereas rabbit serum raised against the whole M+ strain did not. Of note, inhibition of adherence by sIgA occurred despite a much lower immunreactivity against the M6 protein as compared to the hyperimmune serum against the whole M+ strain. The M protein does probably not mediate the adherence of group A streptococci to respiratory cells, as shown by previous studies. However, since the isogenic M- derivative was less invasive to human pharyngeal cells than the M+ strain, our invasion experiments suggest that the M protein may play a role in internalization of group A streptococci into eukaryotic cells. More importantly, internalization and not adherence could be blocked by rabbit serum immunized with recombinant M6 protein.

[Immunoenzyme test system for detecting antibodies to group-specific antigens of group A Streptococcus on the base of conjugated N-acetylglucosamine and its use in medical practice]

Enzyme immunoassay kit has been created for detecting antibodies to group A Streptococcus, based on N-acetylglucosamine. N-acetylglucosamine was selected as the group-specific determinant due to the structure of group A Streptococcus polysaccharide, in which this monosaccharide residue is lateral to the main polysaccharide chain and hence more available for antibodies. Water-soluble polyacrylamide is the carrier in this kit, for this carrier is stable and not liable to nonspecific reaction with proteins. In addition, the synthesis of polyacrylamide conjugates ensures reproducible results. Use of this kit permits the identification of group A streptococcal etiology of the disease and thus carry out appropriate therapy; moreover, it helps predict the outcome of an acute streptococcal infection and detect the poststreptococcal complications in the early period of the disease.

Elevated IgG titer against the C region of streptococcal M protein and its immunodeterminants in patients with poststreptococcal acute glomerulonephritis

OBJECTIVE

To determine the immune responses to the streptococcal M protein in patients with poststreptococcal acute glomerulonephritis (PSAGN).

STUDY DESIGN

The gene coding type 12 M protein of group A streptococcus (M12), a known PSAGN-associated serotype, was cloned and expressed in Escherichia coli to investigate the specific immune responses to the M12 protein in patients with PSAGN. Recombinant M proteins for the variable N-terminal half (AB region) and conserved C-terminal half (C region) were produced separately. IgG titers against each region were measured by enzyme-linked immunosorbent assay in patients with PSAGN (n = 51), uncomplicated streptococcal pharyngitis (n = 26), chronic glomerulonephritis (n = 10), and in healthy control subjects (n = 51). Immunodominant domains within the M protein in PSAGN were further investigated by use of overlapping synthetic peptides.

RESULTS

IgG titers against the C region, but not the AB region, were markedly higher in the PSAGN group than in other groups (p < 0.01), and these titers were maintained for at least several months after antistreptolysin O or antistreptokinase levels had returned to normal. Studies with overlapping synthetic peptides demonstrated that increased IgG reactivity was observed against the C repeat blocks.

CONCLUSION

IgG titers against the C region are significantly elevated in patients with PSAGN, and it may be a diagnostic marker for PSAGN.

Antibody response to Arcanobacterium haemolyticum infection in humans

Arcanobacterium haemolyticum causes pharyngitis, exanthema, and other infections. The evidence of the pathogenicity of A. haemolyticum depends on clinical descriptions of culture-positive patients and a comparison of carrier rates of patients with pharyngitis and healthy, matched controls. In this investigation, the antibody response of the host was studied for the first time, using SDS-PAGE and Western blot analyses. Paired acute and convalescent sera showed development of antibodies to A. haemolyticum in 7 of 8 patients. The antibodies reacted primarily with four distinct cell wall-associated proteins with estimated molecular masses of 80, 60, 50, and 30 kDa. Moreover, the reactivity of convalescent sera from 19 patients was compared with that of sera from 19 controls. Antibodies to A. haemolyticum were found in sera from 16 patients and 6 controls (P < .005); the antibody response of the patients was strong compared with that of the controls. These results indicate that A. haemolyticum infection induces an antibody response in the host.