The erythrocyte and epithelial cell receptors for Haemophilus influenzae are expressed independently

Blood Groups in Infection and Host Susceptibility

Blood group antigens represent polymorphic traits inherited among individuals and populations. At present, there are 34 recognized human blood groups and hundreds of individual blood group antigens and alleles. Differences in blood group antigen expression can increase or decrease host susceptibility to many infections. Blood groups can play a direct role in infection by serving as receptors and/or coreceptors for microorganisms, parasites, and viruses. In addition, many blood group antigens facilitate intracellular uptake, signal transduction, or adhesion through the organization of membrane microdomains. Several blood groups can modify the innate immune response to infection. Several distinct phenotypes associated with increased host resistance to malaria are overrepresented in populations living in areas where malaria is endemic, as a result of evolutionary pressures. Microorganisms can also stimulate antibodies against blood group antigens, including ABO, T, and Kell. Finally, there is a symbiotic relationship between blood group expression and maturation of the gastrointestinal microbiome.

[Blood groups and structure-activity relations]

In the recent years, advances in biochemistry and molecular genetics have contributed to establish the structure of the genes and proteins from most of the 23 blood group systems presently known. From these findings, five functional classes of molecules can be schematically distinguished: (i) transporters and channels, (ii) receptors for ligands, viruses, bacteria and parasites, (iii) adhesion molecules, (iv) enzymes, and (v) structural proteins. Recent advances on these molecules will be reviewed, particularly by illustrating available structure-function relationships.

Specific binding of Haemophilus influenzae to minor gangliosides of human respiratory epithelial cells

Gangliosides are sialylated glycosphingolipids that serve as receptors for various bacteria. To investigate endogenous gangliosides of human respiratory epithelial cells as potential receptors for Haemophilus influenzae, three strains, including nontypeable H. influenzae (NTHI) 1479, and isogenic fimbriated (f+) and nonfimbriated (f0) H. influenzae type b 770235, were 3H labeled and overlaid on two-dimensional thin-layer chromatography (TLC) plates containing either purified HEp-2 gangliosides or murine brain gangliosides. NTHI 1479 bound exclusively to two distinct minor ganglioside doublets, with mobilities near that of GM1. These minor gangliosides comprised only 14.2 and 9.4% of the total, respectively. NTHI 1479 also bound to a distinct ganglioside of human macrophages whose chromatographic mobilities closely resemble those of one of the NTHI-binding gangliosides of HEp-2 cells. H. influenzae type b 770235 f+ and f0 each bound to a different minor HEp-2 ganglioside doublet, with proportionately weaker affinity for a major ganglioside doublet. Remarkably, none of the three strains bound to any murine brain gangliosides. Moreover, when 80 to 90% of sialic acid residues were enzymatically removed from HEp-2 gangliosides, NTHI 1479 binding was proportionately impaired, compared with untreated controls. Our findings support a role for specific gangliosides of specific cells as receptors for H. influenzae strains. Our findings further demonstrate that individual minor gangliosides possess unique biological properties.

Lutheran antigens, CD44-related antigens, and Lutheran regulatory genes

The Lutheran (Lu) blood group antigens are a family of human erythrocyte antigens which reside on two closely-related erythrocyte integral membrane proteins. Sixteen Lutheran or so-called para-Lutheran antigens have thus far been described, and human antisera to many of them have been shown to immunoblot two proteins, of 78 and 85 kDa. Lu cDNA encodes an integral membrane protein of 597 amino acids that is a member of the Ig superfamily. Lu proteins comprise five Ig superfamily domains, along with a single transmembrane domain and a cytoplasmic domain of about 60 amino acids. The two proteins seen in biochemical studies of red cell membranes appear to be derived from 2 mRNA species that differ only in their 3' ends, suggesting that they arise from alternate splicing of a single preRNA. Three genetic backgrounds for the Lu(a-b-) [Lu null] phenotype have been described. A recessive Lu null phenotype is rarely observed as a result of homozygosity for two amorphic LU alleles. However, the most common Lu(a-b-) phenotype appears to be caused by an independently segregating, dominant gene, designated In (Lu), which inhibits expression of all Lutheran antigens to nearly undetectable levels. This gene also affects the expression of other cell surface proteins and blood group antigens that are genetically unlinked to the Lutheran locus, including CD44 and MER2. CD44, a member of the cartilage link family of proteins, bears the In and AnWj blood group antigens. A widely distributed protein CD44 is expressed at normal levels on all tissues except erythrocytes in the presence of the In (Lu) gene. A second Lutheran regulatory gene, XS2, is responsible for the third Lu(a-b-) phenotype, which exhibits an X-linked inheritance pattern. The XS2 gene down-regulates but does not abolish expression of LU genes and does not affect expression of CD44.

Hemagglutination by Pasteurellaceae isolated from rodents

Pasteurellaceae notably P. pneumotropica, have been associated with severe outbreaks of respiratory disease in several species of rodents. Host-specific parasitism of Pasteurellaceae in rodents has hardly been studied. Since host tropism in many bacteria involves adhesive mechanisms, we examined the hemagglutinating (HA) properties of 44 isolates from different rodent species (mouse (15) rat (8), hamster (9), gerbil (10) and Mastomys (2)). Only 13 mouse isolates and the 2 Mastomys isolates hemagglutinated human (type O Rh+) and canine red blood cells (RBCs). No HA was found using RBCs from 10 other animal species. HA was not inhibited by simple sugars and glycoconjugates, but was completely inhibited by heating of bacterial cells for 10 min at 80 or 100 degrees C, partially inhibited by glutaraldehyde and inhibited in a dose-dependent mode by NaIO4, suggesting the involvement of bacterial polysaccharide structures in the HA process. Enrichment procedures did not reveal the presence of HA- subpopulations in HA+ isolates or the presence of HA+ subpopulations in HA- isolates. Electron microscopy revealed the presence of fimbriae both in HA+ and HA- isolates. A regularly structured (RS) layer was detected on cells of part of the HA+ isolates only. Our results suggest that Pasteurellaceae of mice and Mastomys may be related and differ from isolates isolated from other rodent species.

Comparison of hemagglutinating pili of Haemophilus influenzae type b with similar structures of nontypeable H. influenzae

Thirty-eight clinical isolates of nontypeable Haemophilus influenzae were tested for the presence of hemagglutinating pili similar to those of H. influenzae type b (Hib) that mediate buccal epithelial cell adherence. Four endogenously hemagglutinating (HA+) strains were identified, and eight additional HA+ variants were obtained from HA- strains by erythrocyte enrichment. All 12 HA+ nontypeable H. influenzae isolates bound antisera directed against denatured pilins of Hib, but none bound antisera against assembled native pili of Hib. In erythrocyte- and buccal-cell-binding assays, HA+ nontypeable H. influenzae binding was reduced compared with HA+ Hib binding and was not significantly different from HA- nontypeable H. influenzae binding. Both HA- and HA+ nontypeable H. influenzae binding was increased over binding of HA- Hib. HA+ nontypeable H. influenzae strains agglutinated adult erythrocytes that possess the Anton antigen, which is thought to be the receptor for Hib pili, and did not agglutinate cord or Lu(a-b-) dominant erythrocytes, which lack the Anton antigen. Electron microscopy of HA- and HA+ variants of three nontypeable H. influenzae strains showed few or no surface appendages on the HA- organisms, but piluslike structures were seen on many organisms from two HA+ nontypeable H. influenzae strains and on a few organisms from one strain. Thus, nontypeable H. influenzae appears to possess structures that are immunologically similar to the pilins that make up the hemagglutinating pili of Hib. However, nontypeable H. influenzae appears to also possess mechanisms for erythrocyte and buccal cell adherence that are not directly correlated with the presence of a hemagglutinating pilus.

A family showing inheritance of the Anton blood group antigen AnWj and independence of AnWj from Lutheran

A 43-year-old Arab woman was found to be negative for the high incidence AnWj antigen and her serum contained anti-AnWj. Two of her seven siblings were also AnWj-negative, which provides evidence for the first time that the AnWj-negative phenotype may be an inherited character. Blood groups of the family, in which the parents of the proposita are consanguineous, show that AnWj is not part of the ABO, Rh, MNSs, Kell, Duffy, Kidd, Xg and, notably, Lutheran blood group systems and neither is it X or Y linked.

Blocking of fimbria-mediated adherence of Haemophilus influenzae by sialyl gangliosides

The structure of the receptor for the fimbriae of Haemophilus influenzae on human oropharyngeal epithelial cells and erythrocytes was determined in inhibition experiments with various sugars, glycolipids, and glycoproteins. Of 30 monosaccharides and disaccharides at a concentration of 0.1 M and of 3 polysaccharides at a concentration of 1 mg/ml, none inhibited fimbria-specific adherence and hemagglutination. Inhibition was obtained with gangliosides GM1, GM2, GM3, and GD1a in nanomolar concentrations, whereas the asialo derivative of GM1, sialyl-lactose, and sialoglycoproteins were poor inhibitors. These findings indicate that sialyl-lactosylceramide (GM3) is the minimal structure for the fimbria-dependent binding of H. influenzae to its receptor on oropharyngeal epithelial cells and erythrocytes. As is the case with GM2, substitution of GM3 with N-acetylgalactosamine makes the molecule a 10-fold-better receptor analog.

Effect of fusafungine on adherence of Haemophilus influenzae type b to human epithelial cells in vitro

Haemophilus influenzae, a normal host of the nasopharynx of humans, may become a pathogen. The first step of infection is adherence to epithelial cells of the nasopharynx through glycopeptidic adhesins, or pili. Adherence to human epithelial cells in continuous lines, HeLa and Hep2, of 8 piliated strains of Haemophilus influenzae isolated from human infections of the respiratory tract was studied in vitro in the presence of fusafungine, a local bacteriostatic antibiotic. When the bacteria were grown in the presence of 0.5 x the MIC, fusafungine afforded 45-75% of adherence inhibition, but this inhibitory effect did not parallel the MICs. In contrast, no significant effect could be observed either when epithelial cells were exposed to 0.5 x the MIC before use in the adherence assay, or when this assay was performed in the presence of 0.5 x the MIC of fusafungine. The partial adherence inhibition observed suggests that fusafungine interacts with the bacterial binding sites but that other mechanisms may contribute to the inhibitory process. This effect of fusafungine should prevent but not eradicate colonization of the nasopharyngeal mucosa by Haemophilus influenzae and may account for the therapeutic efficacy reported in infections of the respiratory tract due to Haemophilus influenzae.

Combined inheritance of epithelial and erythrocyte receptors for Haemophilus influenzae

Haemophilus influenzae type b expressing fimbriae showed no adherence to buccal epithelial cells and no agglutination of erythrocytes from three AnWj-negative siblings in one family. Hemagglutination of erythrocytes from 13 AnWj-positive members of the same family and from 24 controls was normal, and H. influenzae adhered well to buccal epithelial cells from them. These data indicate that the expression of epithelial and erythrocyte receptors for H. influenzae is inherited concomitantly. Combined with previous data (L. van Alphen, J. Poole, L. Geelen, and H. Zanen, Infect. Immun. 55:2355-2358, 1987), the results show that the receptor molecules on the surfaces of the epithelial cell and the erythrocyte are different but that the binding sites for the fimbriae of H. influenzae are similar.

Cloning and expression in Escherichia coli of LKP pilus genes from a nontypeable Haemophilus influenzae strain

Nontypeable Haemophilus influenzae HF0295, isolated by aspiration from the middle ear of a patient with otitis media, expresses long, thick, and hemagglutinating pili of a single serotype (LKP1) on its surface. An intact pilus vaccine consisting of the LKP1 serotype protected chinchillas against experimental otitis media (C. C. Brinton, Jr., M. J. Carter, D. B. Derber, S. Kar, J. A. Kramarik, A. C. C. To, S. C. M. To, and S. W. Wood, Pediatr. Infect. Dis. J. 8:554-561, 1989; R. B. Karasic, D. J. Beste, S. C. M. To, W. J. Doyle, S. W. Wood, M. J. Carter, A. C. C. To, K. Tanpowpong, C. D. Bluestone, and C. C. Brinton, Jr., Pediatr. Infect. Dis. J. 8:562-565, 1989). The genes encoding LKP1 pili were cloned from a genomic library of the clinical strain as a 12.5-kilobase insert on a plasmid vector and inserted into Escherichia coli K-12. Transposon mutagenesis and deletion constructs mapped the pilus-coding region within a 7-kilobase region of insert DNA. The recombinant bacteria were found by electron microscopy to express pili morphologically similar to LKP1 pili. Purified pilus rods from the recombinant and its parental strain were composed of a single detectable protein with an apparent molecular weight of 27,500. Antibodies raised against LKP1 pili purified from H. influenzae immunologically reacted with pili from the recombinant bacteria. Pili from both strains also adhered to human erythrocytes and buccal cells with the same specificity.

The complete primary structure of pilin from Haemophilus influenzae type b strain Eagan

Adherence of Haemophilus influenzae type b (Hib) to human oropharyngeal cells is mediated by pili which are proteinaceous filaments that extend outward from the bacterial cell surface. Pili from Hib strain Eagan were purified, and the primary structure of the major subunit, pilin, was determined. Sequencing of overlapping peptides showed the mature protein to be comprised of 196 amino acids and to have an Mr of 21,152. The amino terminal sequence was found to be homologous with the sequence previously reported for Hib strain M43 and also to have significant homology to pilins of other gram-negative pathogenic bacteria. Furthermore, Hib pilin had two cysteinyl residues in the amino terminal portion of the protein which were separated by 40 residues (positions 21 and 61); a motif found in other bacterial pilins. The data show that Hib pilin has structural features common to other bacterial pilins.

Regulator genes affecting red cell antigens

Several mechanisms may be involved to explain the action of genes that regulate the expression of red cell antigens. When carbohydrate antigens are involved, lack of an enzyme in the biochemical pathway prevents formation of the precursor for the next and following steps of that path, or, alternatively, addition of an extra sugar to the immuno-dominant sugar may produce a new structure in which the expression of the expected antigen is masked. Thinking of genetic rather than biochemical interference, a regulator gene may "switch-off" the action of a structural gene, and this mechanism could involve the upset of repressor and/or derepressor genes. The mechanisms for the regulator genes described in this article are unknown. The effect of XGR is limited to red cells: the expression of 12E7 antigen on other tissues and cells, other than red cells, is invariable. The reported effects of XOr and XQ are for red cells, but it is unlikely that other cells and tissues have been studied intensively; propositi with these regulator genes are much rarer than people informative for XGR and In(Lu). The effects of In(Lu) are not limited to red cells but have been shown to regulate the expression of p80 on some white cells. Most of the abnormalities in Rhnull cells appear to be associated with the lack of the Rh antigens and lack of Rh proteins. The hypothesis of a functional complex involving Rh, lack of which affects incorporation of apparently unrelated proteins into the red cell membrane, is an attractive idea. Studies of the similar phenotype, Rhmod, suggest that some Rh specificities can be present in cells that appear to be as abnormal, serologically and morphologically, as Rhnull cells. Perhaps some polypeptides are functionally more important than others and perhaps all polypeptides required for the functional efficiency of the Rh complex have not yet been identified. Lack of Lutheran antigens is not always accompanied by modification of other red cell antigens. As suggested by Telen and green, if In(Lu) acts via a single mechanism, then that mechanism differs from that of XS2. Certainly the mechanisms of In(Lu) and XS2 differ in their action on the expression of CD44 or p80 antigens. The red cell surface is well charted territory, familiar to serologists, immunologists, biochemists, and geneticists. It still provides an excellent model for study of cell surface antigens and for the regulator genes described above that modify expression of some red cell antigens.(ABSTRACT TRUNCATED AT 400 WORDS)

Relationship of Haemophilus influenzae type b pilus structure and adherence to human erythrocytes

Six strains of Haemophilus influenzae type b, some expressing immunologically different pili, showed identical patterns of binding to erythrocytes that were characterized for 38 blood group antigens. All six strains appeared to bind to the Anton antigen, as they agglutinated all erythrocytes tested except cord erythrocytes and those characterized as Lu(a-b-), dominant type, including Anton-negative cells.

Interaction of Haemophilus influenzae with human erythrocytes and oropharyngeal epithelial cells is mediated by a common fimbrial epitope

The role of fimbriae in the adherence of Haemophilus influenzae to oropharyngeal epithelial cells and the hemagglutination (HA) of human Anton-positive erythrocytes was examined. HA of bacteria was lost after shearing. Fimbriae purified from the extracellular fluid caused HA and bound to oropharyngeal epithelial cells, as analyzed with immunoperoxidase staining, in a way which was similar to the adherence of bacteria to these cells: binding was over the entire surface of the cells and showed cell-to-cell variation. The specific role of fimbriae in HA and adherence was further examined by inhibition experiments with monoclonal antibodies elicited against the isolated fimbriae. These monoclonal antibodies bound along the entire length of the fimbriae, as seen by immunogold electron microscopy. The monoclonal antibodies and their Fab fragments inhibited HA (reduction in titer from 1:512 to 1:128 and 1:64, respectively) and inhibited the adherence of the homologous H. influenzae strain and of three of eight heterologous H. influenzae strains to oropharyngeal epithelial cells. These results indicate that fimbriae are involved in adherence and HA and that the binding site for the monoclonal antibodies on the fimbriae is not common on all strains.