Secretory immunoglobulin A carries oligosaccharide receptors for Escherichia coli type 1 fimbrial lectin.

Type 1 fimbriae with mannose-specific lectins are widely distributed among members of the family Enterobacteriaceae and confer the ability to attach to a range of host cells, including colonic epithelial cells. The mucosal surfaces are protected by secretory immunoglobulin A (IgA), which agglutinates microorganisms and prevents their attachment to host epithelial cells. This action has been attributed to a specificity of the antigen-combining site of mucosal immunoglobulins for bacterial and viral surface components. Here, we report a novel mechanism for the antibacterial effect of secretory IgA. Secretory IgA and IgA myeloma proteins, especially those of the IgA2 subclass, were shown to possess carbohydrate receptors for the mannose-specific lectin of type 1-fimbriated Escherichia coli. The presence of the high-mannose oligosaccharide chain Man alpha 1-6(Man alpha 1-3)Man alpha 1-6(Man alpha 1-3)Man beta 1-4GlcNAc beta 1-4GlcNAc correlated with binding activity. The interaction between bacterial mannose-specific lectins and IgA receptor oligosaccharide resulted in agglutination of the bacteria and in inhibition of bacterial attachment to colonic epithelial cells. Thus, this interaction could form the basis for a broad antibacterial function of secretory IgA against enterobacteria regardless of the specificity of antibody molecules.

Gamma-globulin treatment of recurrent acute otitis media in children.

This study examined the hypothesis that children prone to acute otitis media have a reduced concentration of circulating antibodies of the IgG2 subclass and that this defect can be compensated for by gamma-globulin treatment. Infants and children below 18 months of age with at least three episodes of acute otitis media were randomized to intramuscular gamma-globulin or no treatment and were followed for 6 months. We could demonstrate neither reduced IgG2 nor specific anti-polysaccharide antibody activity in the otitis-prone children. In contrast they had higher concentrations of IgG2 and antibodies to phosphorylcholine than did age-matched controls. There was neither a relationship between the IgG2 concentration and the number of otitis episodes prior to enrollment nor a reduction in otitis frequency in the gamma-globulin-treated group.

High anti-phosphorylcholine antibody levels and mortality associated with pneumonia.

Phosphorylcholine is an immunodominant determinant of pneumococcal teichoic acids. Antibodies to phosphorylcholine are naturally occurring in man and decline in amount with age. Since antibodies to phosphorylcholine are markers of the immune responsiveness to polysaccharides and since anti-polysaccharide antibodies are highly protective against most bacterial pneumonia we expected a higher rate of pneumonia in elderly individuals with low levels of antibodies to phosphorylcholine. The relationship between the levels of antibodies to phosphorylcholine and mortality was analyzed prospectively in a representative sample of elderly individuals. A significant anti-phosphorylcholine antibody response occurred in a subgroup of the probands. There was a strong association (p less than 0.0001) between high levels of antibodies to phosphorylcholine in the serum at 70 years of age and pneumonia related death up to 14 years later. A similarly strong association was not observed between mortality and the antibody titer to another naturally occurring polysaccharide antigen: the blood group B antigen. Furthermore, there was no association between mortality due to diseases other than pneumonia and the levels of antibodies to phosphorylcholine. The association between antibody levels and subsequent fatal pneumonia provides a means of detecting individuals at risk for pneumonia-related death.

Bacteriuria in representative population samples of persons aged 72-79 years.

Screening for bacteriuria was performed between 1984 and 1988 in persons aged 72-79 years representative of the general population in Göteborg, Sweden. The frequency of bacteriuria (greater than or equal to 10(5)/ml) at a single screening was 6% and 16% at age 72 years and 6% and 14% at age 79 years for the screened men (n = 235 and 259) and women (n = 259 and 297), respectively. By repeated screening after one month and 30 months of those previously negative at age 72 years, an additional 4% and 3% of men and 3% and 7% of women with bacteriuria were detected. Bacteriuric persons were excluded from further screening and controlled by frequent cultures during several years, with careful monitoring of clinical interventions. The persistence of untreated bacteriuria was analyzed in relation to bacterial species and number in the untreated subgroup of bacteriuric individuals. Nine of 10 Escherichia coli (E. coli) with less than 10(6)/ml and 22/22 non-E. coli strains disappeared spontaneously. In contrast, 20/26 (77%, p less than 0.01) with greater than or equal to 10(6) E. coli/ml persisted. Of 17 persons with bacteriuria persisting at least 12 months, 16 were women and 16 had E. coli. Of 201 E. coli cultures obtained from this group, 94% had greater than or equal to 10(6)/ml, and 99% had greater than or equal to 5 x 10(5)/ml. The results indicate that screening for high counts (greater than 10(6)/ml) of E. coli most effectively detects persisting bacteriuria in the general elderly population.

Influence of P blood group phenotype on susceptibility to urinary tract infection.

Bacterial attachment is an important event in the pathogenesis of urinary tract infection (UTI). Increased receptivity on the host cells has been suggested influence proneness to infection. The dual function of the globoseries of glycolipids both as receptors for attaching E. coli and as P blood group antigens lead us to examine the P blood group phenotype distribution in UTI prone patient populations. A correlation between the P1 blood group phenotype and susceptibility to UTI was found. Patients with recurrent pyelonephritis had 74/79 (94%), P1 compared to 75% in healthy controls. In contrast patients with asymptomatic bacteriuria (ABU) had a reduced frequency of P1, 43/74 (58%). P1 and P2 individuals differ in amount and composition of the globoseries of glycolipids on their erythrocytes. A similar difference in other tissues, e.g. uroepithelial cells might explain the association of P1 with UTI. There was, however, no significant difference in bacterial adherence to uroepithelial cells from P1 and P2 individuals. Other mechanisms explaining the increase in P1 individuals in recurrent pyelonephritis are discussed.

Host response in women with symptomatic urinary tract infection.

The agreement between clinical signs and host response was analysed in 174 women with symptomatic urinary tract infection. C-reactive protein (CRP) confirmed the clinical diagnosis in that 94% of non-pregnant and 91% of pregnant women with acute pyelonephritis had serum levels greater than or equal to 30 mg/l, compared with only 5% of cystitis patients. There was a significant increase in the erythrocyte sedimentation rate (ESR) and reduction of the renal concentrating capacity in patients with acute pyelonephritis, although the overlap with the cystitis group was greater than for CRP. The transient decrease in urine osmolality was unrelated to age, as were CRP, ESR and the total white blood cell count. Pregnant women had higher ESR but lower CRP levels than non-pregnant women with acute pyelonephritis. The renal concentrating capacity was more reduced in those infected with Escherichia coli expressing adhesins specifically recognizing Gal alpha 1----4Gal beta-containing receptors on uroepithelial cells.

Bacterial adhesion as an indicator of renal involvement in bacteriuria of pregnancy.

The association of bacterial virulence with the host response to bacteriuria was evaluated in 70 pregnant women with acute pyelonephritis or bacteriuria detected at screening. Patients infected with Escherichia coli attaching to Gal alpha 1----4Gal beta-containing receptors, had significantly higher levels of C-reactive protein and lower renal concentrating capacity than patients infected with strains lacking this specificity. The renal concentrating capacity ranged from 419-1151 mOsm/kg in the women with bacteriuria on screening. 5/11 women with a renal concentrating capacity less than or equal to 784 mOsm/kg were infected with Gal alpha 1----4Gal beta-specific bacteria, compared to 0/16 of patients who concentrated the urine greater than 784 mOsm/kg. According to earlier studies the risk for progression to pyelonephritis and recurrences during pregnancy was increased in bacteriuric women with a reduced renal concentrating capacity. The present study demonstrates that this risk group can be identified in part by the properties of the infecting E. coli strains.

Fever, bacteriuria and concomitant disease in children with urinary tract infection.

A total of 124 children aged 0.2 to 6 years were enrolled in a study of first time febrile urinary tract infection. The patient population was stratified in groups according to the stringency of criteria for fever and bacteriuria and the presence of concomitant disease. The major group of 88 patients consisted of children with fever greater than or equal to 38.5 degrees C measured at the hospital within 24 hours of diagnosis, bacteriuria verified by suprapubic bladder aspiration or repeated cultures of voided urine, but without concomitant disease. These children were mainly infected with attaching Escherichia coli specific for galactose alpha (1----4) beta galactose containing receptors and had laboratory evidence of inflammation. Another group of 11 children were distinguished with strictly defined bacteriuria and concomitant disease. These children were infected with nonattaching bacteria and had lower concentrations of C-reactive protein in serum and lower microsedimentation rates than the major group. Five of these children had a reduction in renal concentrating capacity. The study emphasizes the heterogeneity among patients with fever and bacteriuria but does not rule out the possibility of renal involvement in any subgroup.

Attachment of Escherichia coli via mannose- or Gal alpha 1----4Gal beta-containing receptors to human colonic epithelial cells.

The role of bacterial adhesion for the maintenance of the large-intestinal microflora has not been established. In this study, colonic cells from the adenocarcinoma cell line HT-29 or from surgical specimens were tested for the ability to bind Escherichia coli. The E. coli strains were manipulated by transformation or by mutagenesis to express either mannose-specific type 1 fimbriae (strains 506 MS and HU742) or Gal alpha 1----4Gal beta-specific P fimbriae (506 MR and HU824). Binding to HT-29 cells was seen with strains of either receptor specificity and was inhibited by alpha-methyl mannoside or globotetraosylceramide (GalNAc beta 1----3Gal alpha 1----4Gal beta 1----4Glc-ceramide), respectively. The Gal alpha 1----4Gal beta-specific strains interacted with a loosely surface-associated substance, which was sensitive to mechanical treatment and incubation at 37 degrees C, while the mannose-specific strains bound both directly to the cell and to the loosely associated substance. Isolated colonic epithelial cells bound the mannose-specific bacteria in high numbers, while the attachment of the Gal alpha 1----4Gal beta-specific strains depended on the elution method. Cells eluted sequentially with magnetic stirring were unable to bind the Gal alpha 1----4Gal beta-specific bacteria, while elution by a more gentle method resulted in binding of these strains to material loosely associated with the epithelial cells. Thus, the binding pattern of isolated colonic epithelial cells paralleled that of the HT-29 cell line. Conceivably, binding to mannose- and Gal alpha 1----4Gal beta-containing receptors could contribute to the maintenance of E. coli in the human large intestine.

Protein serotyping of Streptococcus pneumoniae based on reactivity to six monoclonal antibodies.

Six monoclonal antibodies to proteins of Streptococcus pneumoniae were tested in a dot blot assay for reactivity with 499 clinical isolates of pneumococci. Forty-four percent of the isolates reacted with at least one of the antibodies. Nineteen patterns of reactivity were identified and each designated as a provisional protein serotype. Protein serotyping identified pneumococcal strains independently of their capsular type and made it possible to differentiate strains within most capsular types. A protein serotyping system provides a new dimension to the phenotypic identification of S. pneumoniae and may eventually provide a basis for assessing the population structure of these organisms.

Globo-A--a new receptor specificity for attaching Escherichia coli.

Uropathogenic Escherichia coli strains designated as ONAP, based on their O negative A positive agglutination of human P1 erythrocytes, were shown to prefer the globo-A glycolipid as a receptor structure. The dependence on both the A terminal and the globoseries chain was confirmed by agglutination of human AP1, but not Ap or OP1 erythrocytes and by binding to the globo-A glycolipid on TLC plates. Neither Gal alpha 1----4Gal beta nor the A trisaccharide GalNAc alpha 1----3(Fuc alpha 1----2)Gal beta alone functioned as receptors. The bacteria thus appeared to recognize an epitope resulting from the combination of the terminal and internal structures.

Bacterial attachment and inflammation in the urinary tract.

The mechanism whereby attachment enhances Escherichia coli virulence in the urinary tract was studied by a detailed analysis of the host response to bacteriuria. Episodes of bacteriuria in 1473 children were followed prospectively from 1970 to 1984. To study the inflammatory response to the bacteriuric epidoses, we recorded body temperature, C-reactive protein, microsedimentation rate, urinary leukocyte count, and renal concentrating capacity. Bacterial isolates from each episode were identified and saved, and the adhesive capacity of 2669 E. coli strains was defined by their binding to galactose alpha 1----4galactose beta-containing receptors. Inflammatory response was significantly higher and renal concentrating capacity significantly lower during episodes caused by attaching strains. There was a linear relation between the number of indicators of inflammation and the proportion of galactose alpha 1----4galactose beta-binding strains present. Vesicoureteric reflux potentiated the inflammatory response. Attaching strains of E. coli thus appeared to be more capable of causing inflammation than were other bacteria. The potentiating effect of attachment on inflammation explains the over-representation of galactose alpha 1----4galactose beta-recognizing bacteria in patients with acute pyelonephritis.

Role of adherence of Streptococcus pneumoniae in acute otitis media.

The adherence of Streptococcus pneumoniae to human nasopharyngeal epithelial cells was studied as a possible determinant in the development of acute otitis media (AOM). Pneumococcal isolates were obtained from the nasopharynx (NP) and middle ear fluid of infants followed from birth in a prospective study of pneumococcal carriage and infection. The adherence of 33 middle ear fluid isolates from 19 infants with AOM was compared with 143 strains recovered from NP cultures taken from each child both at the time of their acute infections and on other occasions. We studied 171 NP isolates from 29 "carrier" infants, who had no pneumococcal infections, for comparison. Adherence properties were not associated with any particular pneumococcal capsular types, nor were adherent strains more frequent among infants with AOM. There was no evidence to support the hypothesis that pneumococci associated with AOM have a special propensity for adherence. Adherence was a frequent characteristic of pneumococci recovered from the NP, especially in connection with upper respiratory tract infection, and may be required for the establishment of colonization but was not a property that discriminated between carriage strains and those causing AOM.

Host resistance to mucosal gram-negative infection. Susceptibility of lipopolysaccharide nonresponder mice.

The effect of Lps on the resistance of mice to gram-negative infection was compared in two genetically different backgrounds; C3H and C57BL. To mimic the natural sequence of pathogenetic events, infection was induced via a mucosal surface (intravesically), with Escherichia coli which remained at the mucosal site and Salmonella typhimurium which invaded to e.g., livers and spleens. Susceptibility was assessed as the bacterial persistence in kidneys, bladders, livers, and spleens at various times after infection. The initial clearance of both bacterial species from the mucosal site was significantly impaired in Lpsd mice both in the C3H and C57BL backgrounds. In the C57BL mice, additional unknown determinants conferred increased resistance to mucosal infection compared to the C3H mouse. For S. typhimurium, these resistance factors and alleles at the Lps locus dominated over Ity as determinants of resistance to mucosal infection. The Itys genotype conferred a significant increase in the susceptibility only to systemic infection, especially in the Lpsd, Itys mice. These results demonstrate an important difference between the genetic determinants of host resistance at mucosal and systemic sites, and emphasize the role of LPS induced host defense mechanisms for bacterial clearance from mucosal surfaces.

Role of attachment for the virulence of Streptococcus pneumoniae.

Adherence of microorganisms to mucosal surfaces is a general phenomenon among microorganisms infecting the human host. Its role for persistence and colonization as well as production of local inflammation is well established. This paper describes the adhesion of Streptococcus pneumoniae to human epithelial cells. Strains from various anatomical sites or diseases are compared for attaching capacity. Isolates from the same host but at different times are also compared. The molecular mechanisms, the so-called adhesin-receptor interactions, are partially described. The pneumococcus recognizes a sugar sequence; GlcNAc beta 1-3Gal; on the surface of the host epithelial cell. Glycoconjugates containing this disaccharide act as receptors for adhering pneumococci. The adhesin in pneumococcal attachment is less well characterized. It is a heat and trypsin sensitive component, most likely a peptide, which forms a bridge between the receptor and an anchoring site in the pneumococcal cell wall. Receptor active saccharides are part of the adhesion-inhibitory activity found in human milk.

Specificity of binding of a strain of uropathogenic Escherichia coli to Gal alpha 1----4Gal-containing glycosphingolipids.

A strain of Escherichia coli originally isolated from urine of a patient with acute pyelonephritis was studied in detail for binding to glycosphingolipids. Bacteria labeled metabolically with [14C]glucose were layered over a glycolipid chromatogram and bound bacteria were detected by autoradiography. The detection was down to a few ng of glycolipid (pmol level) under these assay conditions. At a test level of 500 ng all glycolipids (more than a dozen molecular species analyzed) with Gal alpha 1----4Gal as an internal or terminal part bound the bacteria strongly while glycolipids known to lack this sequence were negative. Conformational analysis using hard sphere calculations including the exo-anomeric effect showed a bend in the saccharide chain at this disaccharide with a largely hydrophobic surface of the convex side, probably being part of the binding epitope. Mixtures of glycolipids isolated from a human ureter scraping and from urinary sediments bound bacteria in the 2- to 7-sugar interval. Thus, this infectious strain of E. coli recognizes glycolipids being present in epithelial cells lining the urinary tract.

Evidence for separate genetic defects in C3H/HeJ and C3HeB/FeJ mice, that affect susceptibility to gram-negative infections.

Past studies have suggested a linkage between susceptibility to Salmonella typhimurium infection and the Lpsd genotype in C3H mice. Recently, this linkage was questioned by the finding that C3HeB/FeJ mice (Lpsn,Lpsn) were highly susceptible to systemic S. typhimurium infection. The present study shows a marked difference between C3H/HeJ and C3HeB/FeJ in their susceptibility to Gram-negative urinary tract infection. The number of E. coli and S. typhimurium recovered from the kidneys 24 hr after infection was 70 to 100 times higher in C3H/HeJ than in C3HeB/FeJ or C3H/HeN mice. Subsequently, in C3HeB/FeJ mice S. typhimurium multiplied to the level of C3H/HeJ mice, resulting in a shorter mean survival time of C3H/HeJ and C3HeB/FeJ compared with C3H/HeN mice. In contrast, E. coli remained localized to the urinary tract of C3H/HeJ mice but were eliminated from C3HeB/FeJ and C3H/HeN mice. Thus, experimental E. coli urinary tract infection appears to provide a method to differentiate the genetic defects of C3H/HeJ and C3HeB/FeJ mice. The results support an influence of the Lpsd genotype on clearance of Gram-negative bacteria from the kidneys of C3H mice.

Protective factors in milk and the development of the immune system.

The neonate is immature in certain immunologic functions. The slow development of secretory immunoglobin A (IgA) seems to be compensated by selective transfer of secretory IgM into exocrine secretions on mucous membranes during the first few months of life. Secretory IgA and secretory IgM antibodies against Escherichia coli and poliovirus are already found in the neonate, possibly in response to the maternal anti-idiotypic IgG antibodies transplacentally exposing the fetus. Via such a mechanism, food antibodies could occur before direct food exposure in the infant. Human milk provides large amounts of antibodies (as a crude comparison, about 50 times the amount of antibodies given to a patient with hypogammaglobulinemia). The milk antibodies, dominated by secretory IgA, protect especially against intestinal infections. The milk also contains oligosaccharide analogues to epithelial receptors for bacteria. They, as well as a number of milk components such as lactoferrin and lysozyme, may contribute to host defense. The food antibodies in human milk may influence the infant's immune response to foreign food proteins introduced during weaning.

Identification of an active disaccharide unit of a glycoconjugate receptor for pneumococci attaching to human pharyngeal epithelial cells.

Glycoconjugates containing the disaccharide unit GlcNAc beta 1 leads to 3Gal beta were suggested as receptors for pneumococci adhering to human pharyngeal epithelial cells. The receptor activity was detected both by inhibition of adhesion by an excess of free oligosaccharide and by induction or increase of adhesion after coating of target cells with glycolipid. Studies with free natural and synthetic oligosaccharides identified the disaccharide GlcNAc beta 1 leads to 3Gal beta as one critical binding site. The specificity of recognition was shown inter alia by the lack of inhibitory activity of GlcNAc beta 1 leads to 4Gal beta, which differs only in the linkage of the two sugars. Specific interference with pneumococcal adhesion by administration of soluble receptor sugar may improve our understanding of the role of adhesion in vivo.