Studies on Gonococcus infection. X. Pili and leukocyte association factor as mediators of interactions between gonococci and eukaryotic cells in vitro

Neisseria gonorrhoeae subverts formin-dependent actin polymerization to colonize human macrophages

Dynamic reorganization of the actin cytoskeleton dictates plasma membrane morphogenesis and is frequently subverted by bacterial pathogens for entry and colonization of host cells. The human-adapted bacterial pathogen Neisseria gonorrhoeae can colonize and replicate when cultured with human macrophages, however the basic understanding of how this process occurs is incomplete. N. gonorrhoeae is the etiological agent of the sexually transmitted disease gonorrhea and tissue resident macrophages are present in the urogenital mucosa, which is colonized by the bacteria. We uncovered that when gonococci colonize macrophages, they can establish an intracellular or a cell surface-associated niche that support bacterial replication independently. Unlike other intracellular bacterial pathogens, which enter host cells as single bacterium, establish an intracellular niche and then replicate, gonococci invade human macrophages as a colony. Individual diplococci are rapidly phagocytosed by macrophages and transported to lysosomes for degradation. However, we found that surface-associated gonococcal colonies of various sizes can invade macrophages by triggering actin skeleton rearrangement resulting in plasma membrane invaginations that slowly engulf the colony. The resulting intracellular membrane-bound organelle supports robust bacterial replication. The gonococci-occupied vacuoles evaded fusion with the endosomal compartment and were enveloped by a network of actin filaments. We demonstrate that gonococcal colonies invade macrophages via a process mechanistically distinct from phagocytosis that is regulated by the actin nucleating factor FMNL3 and is independent of the Arp2/3 complex. Our work provides insights into the gonococci life-cycle in association with human macrophages and defines key host determinants for macrophage colonization.

During infection, the human-adapted bacterial pathogen Neisseria gonorrhoeae and causative agent of gonorrhea can invade the submucosa of the urogenital tract where it encounters tissue-resident innate immune sentinels, such as macrophages and neutrophils. Instead of eliminating gonococci, macrophages support robust bacterial replication. Here, we detail the life cycle of N. gonorrhoeae in association with macrophages and define key regulators that govern the colonization processes. We uncovered that N. gonorrhoeae establishes two distinct subcellular niches that support bacterial replication autonomously–one niche was on the macrophage surface and another one was intracellular. Gonococci subverted the host actin cytoskeleton through the actin nucleating factor FMNL3 to invade colonized macrophages and occupy a membrane-bound intracellular organelle. We propose that N. gonorrhoeae ability to occupy distinct subcellular niches when colonizing macrophages likely confers broad protection against multiple host defense responses.

Seminal plasma initiates a Neisseria gonorrhoeae transmission state

Niche-restricted pathogens are evolutionarily linked with the specific biological fluids that are encountered during infection. Neisseria gonorrhoeae causes the genital infection gonorrhea and is exposed to seminal fluid during sexual transmission. Treatment of N. gonorrhoeae with seminal plasma or purified semen proteins lactoferrin, serum albumin, and prostate-specific antigen each facilitated type IV pilus-mediated twitching motility of the bacterium. Motility in the presence of seminal plasma was characterized by high velocity and low directional persistence. In addition, infection of epithelial cells with N. gonorrhoeae in the presence of seminal plasma resulted in enhanced microcolony formation. Close association of multiple pili in the form of bundles was also disrupted after seminal plasma treatment leading to an increase in the number of single pilus filaments on the bacterial surface. Thus, exposure of N. gonorrhoeae to seminal plasma is proposed to alter bacterial motility and aggregation characteristics to influence the processes of transmission and colonization.

There are greater than 100 million estimated new cases of gonorrhea annually worldwide. Research characterizing the mechanisms of pathogenesis and transmission of Neisseria gonorrhoeae is important for developing new prevention strategies, since antibiotic resistance of the organism is becoming increasingly prevalent. Our work identifies seminal plasma as a mediator of N. gonorrhoeae twitching motility and microcolony formation through functional modification of the type IV pilus. These findings provide insight into motility dynamics and epithelial cell colonization under conditions that are relevant to sexual transmission. Type IV pili are common virulence factors with diverse functions among bacterial pathogens, and this work identifies interactions between type IV pili and the host environment. Finally, this work illustrates the importance of the host environment and niche-specific fluids on microbial pathogenesis.

Phase variation leads to the misidentification of a Neisseria gonorrhoeae virulence gene

Neisseria gonorrhoeae is the causative agent of gonorrhea and an obligate pathogen of humans. The Opa proteins of these bacteria are known to mediate attachment and internalization by host cells, including neutrophils. The Opa protein repertoire of a typical N. gonorrhoeae isolate is encoded on ~11 genes distributed throughout the chromosome and is subject to stochastic changes in expression through phase variation. Together, these characteristics make Opa proteins a critical yet unpredictable aspect of any experimental investigation into the interaction of N. gonorrhoeae with host cells. The goal of this study was to identify novel virulence factors of N. gonorrhoeae by assessing the contribution of a set of uncharacterized hydrogen peroxide-induced genes to bacterial survival against neutrophil-mediated killing. To this end, a strain harboring an engineered mutation in the NGO0322 gene was identified that exhibited increased sensitivity to neutrophil-mediated killing, enhanced internalization by neutrophils, and the ability to induce high levels of neutrophil-generated reactive oxygen species. Each of these phenotypes reverted to near wild-type levels following genetic complementation of the NGO0322 mutation. However, after immunoblot analysis of Opa proteins expressed by the isogenic parent, mutant, and genetically complemented strains, it was determined that phase variation had resulted in a disparity between the Opa profiles of these strains. To determine whether Opa phase variation, rather than NGO0322 mutation, was the cause of the observed neutrophil-related phenotypes, NGO0322 function was investigated in N. gonorrhoeae strains lacking all Opa proteins or constitutively expressing the OpaD variant. In both cases, mutation of NGO0322 did not alter survival of gonococci in the presence of neutrophils. These results demonstrate the importance of controlling for the frequent and random variation in Opa protein production by N. gonorrhoeae when investigating host cell interactions.

The biology of Neisseria adhesins

Members of the genus Neisseria include pathogens causing important human diseases such as meningitis, septicaemia, gonorrhoea and pelvic inflammatory disease syndrome. Neisseriae are found on the exposed epithelia of the upper respiratory tract and the urogenital tract. Colonisation of these exposed epithelia is dependent on a repertoire of diverse bacterial molecules, extending not only from the surface of the bacteria but also found within the outer membrane. During invasive disease, pathogenic Neisseriae also interact with immune effector cells, vascular endothelia and the meninges. Neisseria adhesion involves the interplay of these multiple surface factors and in this review we discuss the structure and function of these important molecules and the nature of the host cell receptors and mechanisms involved in their recognition. We also describe the current status for recently identified Neisseria adhesins. Understanding the biology of Neisseria adhesins has an impact not only on the development of new vaccines but also in revealing fundamental knowledge about human biology.

Opa proteins and CEACAMs: pathways of immune engagement for pathogenic Neisseria

Neisseria meningitidis and Neisseria gonorrhoeae are globally important pathogens, which in part owe their success to their ability to successfully evade human immune responses over long periods. The phase-variable opacity-associated (Opa) adhesin proteins are a major surface component of these organisms, and are responsible for bacterial adherence and entry into host cells and interactions with the immune system. Most immune interactions are mediated via binding to members of the carcinoembryonic antigen cell adhesion molecule (CEACAM) family. These Opa variants are able to bind to different receptors of the CEACAM family on epithelial cells, neutrophils, and T and B lymphocytes, influencing the innate and adaptive immune responses. Increased epithelial cell adhesion creates the potential for prolonged infection, invasion and dissemination. Furthermore, Opa proteins may inhibit T-lymphocyte activation and proliferation, B-cell antibody production, and innate inflammatory responses by infected epithelia, in addition to conferring increased resistance to antibody-dependent, complement-mediated killing. While vaccines containing Opa proteins could induce adhesion-blocking and bactericidal antibodies, the consequence of CEACAM binding by a candidate Opa-containing vaccine requires further investigation. This review summarizes current knowledge of the immunological consequences of the interaction between meningococcal and gonococcal Opa proteins and human CEACAMs, considering the implications for pathogenesis and vaccine development.

Retinoic acid treated HL60 cells express CEACAM1 (CD66a) and phagocytose Neisseria gonorrhoeae

Neisseria gonorrhoeae (gonococci, GC) are phagocytosed by neutrophils through the interaction between opacity proteins (Opa) and the CEA (CD66) family of antigens. In order to study this interaction, we used the human myeloid leukemia HL60 cell line, which differentiates into granulocyte-like cells upon treatment with dimethylsulfoxide (DMSO) or retinoic acid (RA). We found that RA-, but not DMSO- or untreated-HL60 cells, can phagocytose OpaI-expressing gonococci as well as Escherichia coli. The interaction of OpaI E. coli with RA-treated HL60 cells was inhibited by antibodies against CEACAM1. Phagocytosis of OpaI E. coli was found to be a result of the expression of CEACAM1 in RA-treated HL60 cells. Our results indicate that the level of expression of CEACAM1 in HL60 cells can be regulated by treatment with RA in a differentiation-dependent manner, and that this is important for phagocytosis of OpaI-expressing gonococci or E. coli.

Immunoreceptor tyrosine-based activation motif phosphorylation during engulfment of Neisseria gonorrhoeae by the neutrophil-restricted CEACAM3 (CD66d) receptor

Gonorrhea is characterized by a purulent urethral or cervical discharge consisting primarily of neutrophils associated with Neisseria gonorrhoeae. These interactions are facilitated by gonococcal colony opacity-associated (Opa) protein binding to host cellular CEACAM receptors. Of these, CEACAM3 is restricted to neutrophils and contains an immunoreceptor tyrosine-based activation motif (ITAM) reminiscent of that found within certain phagocytic Fc receptors. CEACAM3 was tyrosine phosphorylated by a Src family kinase-dependent process upon infection by gonococci expressing CEACAM-specific Opa proteins. This phosphorylation was necessary for efficient bacterial uptake; however, a less efficient uptake process became evident when kinase inhibitors or mutagenesis of the ITAM were used to prevent phosphorylation. Ligated CEACAM3 was recruited to a cytoskeleton-containing fraction, intense foci of polymerized actin were evident where bacteria attached to HeLa-CEACAM3, and disruption of polymerized actin by cytochalasin D blocked all bacterial uptake by these cells. These data support a model whereby CEACAM3 can mediate the Opa-dependent uptake of N. gonorrhoeae via either an efficient, ITAM phosphorylation-dependent process that resembles phagocytosis or a less efficient, tyrosine phosphorylation-independent mechanism.

The CGM1a (CEACAM3/CD66d)-mediated phagocytic pathway of Neisseria gonorrhoeae expressing opacity proteins is also the pathway to cell death

Phagocytosis of Opa+ Neisseria gonorrhoeae (gonococcus, GC) by neutrophils is in part dependent on the interaction of Opa proteins with CGM1a (CEACAM3/CD66d) antigens, a neutrophil-specific receptor. However, the signaling pathways leading to phagocytosis have not been characterized. Here we show that interaction of OpaI bacteria with neutrophils or CGM1a-transfected DT40 cells induces calcium flux, which correlates with phagocytosis of bacteria. We identified an immunoreceptor tyrosine-based activation motif (ITAM) in CGM1a, and showed that the ability of CGM1a to transduce signals and mediate phagocytosis was abolished by mutation of the ITAM tyrosines. We also demonstrated that CGM1a-ITAM-mediated bacterial phagocytosis is dependent on Syk and phospholipase C activity in DT40 cells. Unexpectedly, the activation of the CGM1a-ITAM phagocytic pathway by Opa+ GC results in induction of cell death.

Interactions of pathogenic neisseriae with epithelial cell membranes

The closely related bacterial pathogens Neisseria gonorrhoeae (gonococci, GC) and N. meningitidis (meningococci, MC) initiate infection at human mucosal epithelia. Colonization begins at apical epithelial surfaces with a multistep adhesion cascade, followed by invasion of the host cell, intracellular persistence, transcytosis, and exit. These activities are modulated by the interaction of a panoply of virulence factors with their cognate host cell receptors, and signals are sent from pathogen to host and host to pathogen at multiple stages of the adhesion cascade. Recent advances place us on the verge of understanding the colonization process at a molecular level of detail. In this review we describe the Neisseria virulence factors in the context of epithelial cell biology, placing special emphasis on the signaling functions of type IV pili, pilus-based twitching motility, and the Opa and Opc outermembrane adhesin/invasin proteins. We also summarize what is known about bacterial intracellular trafficking and growth. With the accelerated integration of tools from cell biology, biochemistry, biophysics, and genomics, experimentation in the next few years should bring unprecedented insights into the interactions of Neisseriae with their host.

Proteoglycan receptor binding by Neisseria gonorrhoeae MS11 is determined by the HV-1 region of OpaA

The interaction of the OpaA protein of Neisseria gonorrhoeae MS11mk with heparan sulphate-containing proteoglycan receptors on Chang conjunctiva epithelial cells was examined using isolated receptor binding and cell adherence/internalization assays. OpaA deletion proteins, in which the four surface-exposed regions of the protein were deleted individually, and chimeric OpaA/B proteins, in which the surface-exposed regions of the OpaA and OpaB proteins were exchanged, were expressed in N. gonorrhoeae. The recombinant deletion proteins and the chimeric OpaA/B proteins were surface exposed in the outer membrane of N. gonorrhoeae. Isolated receptor-binding assays and Chang cell infection assays with OpaA deletion variants indicated that hypervariable region 1 was essential for the interaction of N. gonorrhoeae with the proteoglycan receptor. Expression of chimeric OpaA/B proteins confirmed the central role of hypervariable region 1 in receptor binding and demonstrated that this domain alone confers the invasive biological phenotype in a non-heparan sulphate proteoglycan-binding Opa protein. The other variable regions of OpaA enhanced receptor binding in the presence of region 1, but did not constitute binding domains on their own. The results indicate that proteoglycan receptor binding results from a hierarchical interaction between the variable domains of the OpaA protein of MS11mk.

CD66-mediated phagocytosis of Opa52 Neisseria gonorrhoeae requires a Src-like tyrosine kinase- and Rac1-dependent signalling pathway

The interaction of Neisseria gonorrhoeae with human phagocytes is a hallmark of gonococcal infections. Recently, CD66 molecules have been characterized as receptors for Opa52-expressing gonococci on human neutrophils. Here we show that Opa52-expressing gonococci or Escherichia coli or F(ab) fragments directed against CD66, respectively, activate a signalling cascade from CD66 via Src-like protein tyrosine kinases, Rac1 and PAK to Jun-N-terminal kinase. The induced signal is distinct from Fcgamma-receptor-mediated signalling and is specific for Opa52, since piliated Opa- gonococci, commensal Neisseria cinerea or E.coli do not stimulate this signalling pathway. Inhibition of Src-like kinases or Rac1 prevents the uptake of Opa52 bacteria, demonstrating the crucial role of this signalling cascade for the opsonin-independent, Opa52/CD66-mediated phagocytosis of pathogenic Neisseria.

Differential response of human monocytes to Neisseria gonorrhoeae variants expressing pili and opacity proteins

Experiments in vitro suggest that Neisseria gonorrhoeae surface variation plays a key role in gonococcal pathogenesis by providing the appropriate bacterial phenotypes to go through different stages of the infection. Here we report on the effects of phase and antigen variation of two major gonococcal adhesins, pili and opacity (Opa) outer membrane proteins, on the interaction of the gonococci with human monocytes. Using a set of recombinants of gonococcus strain MS11 that each express 1 of 11 genetically defined Opa proteins or a defined type of pilus, we found that both Opa proteins and pili promote bacterial phagocytosis by monocytes in the absence of serum and that this feature largely depends on the type of protein that is expressed. One of the Opa proteins (Opa[50]) strongly promoted uptake by monocytes but had little effect on the interaction with polymorphonuclear leukocytes under the conditions employed. Similarly, the phagocytosis-promoting effect of the pili was much more pronounced in monocytes than in neutrophils (4-fold versus 22-fold stimulation of uptake, respectively). Only a subpopulation of both types of phagocytes actively ingested bacteria, as has been observed during natural infections. Measurements of luminol-enhanced chemiluminescence demonstrated that phagocytosis of opaque but not piliated gonococci was accompanied by an increase in oxygen-reactive metabolites. These findings demonstrate that the monocyte response towards gonococci is highly dependent on the bacterial phenotype and differs from the neutrophil response. This diversity in bacterial behavior towards various types of human phagocytic cells underlines the biological impact of gonococcal surface variation and may explain previous contradictory results on this subject.

Phenotypic variants of meningococci and their potential in phagocytic interactions: the influence of opacity proteins, pili, PilC and surface sialic acids

In previous studies we have examined the roles of meningococcal surface structures (capsule, lipopolysaccharides, pili and opacity proteins: Opa and Opc) in bacterial interactions with human epithelial, endothelial and mononuclear phagocytic cells. In the current investigations, using defined derivatives of a serogroup A strain C751 and a serogroup B strain MC58, we studied the roles of these structures with human polymorphonuclear phagocytes (PMN). In addition, we examined the potential influence of the pilus-associated protein, PilC, previously known to affect epithelial cell interactions. The data show, that, as with monocytes, opacity proteins affect bacterial interactions with PMN and require surface sialic acids (on capsule and LPS) to be down-modulated in order to function. Also, in contrast to their role in human epithelial and endothelial adherence, neither pili nor PilC expression had any effect on phagocytic cell interactions with respect to induction of chemiluminescence as well as phagocytic killing. Examination of the relative influence of Opa and Opc indicated that Opa proteins are more effective than Opc in PMN interactions whereas the reverse was the case with monocytes. These results suggest that Opa and Opc mediate interactions with phagocytic cells via distinct mechanisms. Observations presented here and reported previously collectively show that the structural requirements of meningococci for interacting with phagocytes, in the absence of opsonins, are present in the phenotype which is often isolated from the nasopharynx (asialylated, piliated, Opa/Opc+) whereas the phenotype prevalent in the blood (sialyted, piliated, Opa/Opc+) retains the ability to adhere to endothelial cells (via pili) but appears to be refractory to interactions with phagocytic cells.

CGM1a antigen of neutrophils, a receptor of gonococcal opacity proteins

Neisseria gonorrhoeae (GC) or Escherichia coli expressing phase-variable opacity (Opa) protein (Opa+ GC or Opa+ E. coli) adhere to human neutrophils and stimulate phagocytosis, whereas their counterparts not expressing Opa protein (Opa- GC or Opa- E. coli) do not. Opa+ GC or E. coli do not adhere to human lymphocytes and promyelocytic cell lines such as HL-60 cells. The adherence of Opa+ GC to the neutrophils can be enhanced dramatically if the neutrophils are preactivated. These data suggest that the components binding the Opa+ bacteria might exist in the granules. CGM1a antigen, a transmembrane protein of the carcinoembryonic antigen family, is exclusively expressed in the granulocytic lineage. The predicted molecular weight of CGM1a is approximately 30 kDa. We observed specific binding of OpaI+ E. coli to a 30-kDa band of polymorphonuclear leukocytes lysates. To prove the hypothesis that the 30-kDa CGM1a antigen from neutrophils was the receptor of Opa+ bacteria, we showed that a HeLa cell line expressing human CGM1a antigen (HeLa-CGM1a) bound Opa+ E. coli and subsequently engulfed the bacteria. Monoclonal antibodies (COL-1) against CGM1 blocked the interaction between Opa+ E. coli and HeLa-CGM1a. These results demonstrate that HeLa cells when expressing the CGM1a antigens bind and internalize OpaI+ bacteria.

Escherichia coli expressing a Neisseria gonorrhoeae opacity-associated outer membrane protein invade human cervical and endometrial epithelial cell lines

Members of the opacity-associated (Opa) outer membrane protein family of Neisseria gonorrhoeae have been proposed to mediate adherence to and invasion of cultured human epithelial cells. We transformed Escherichia coli with a plasmid containing a gonococcal opa gene fused in-frame to the leader sequence of the beta-lactamase gene as described by Palmer et al. [Palmer, L., Brooks, G. F. & Falkow, S. (1989) Mol. Microbiol. 3, 663-671]. These transformed E. coli [E. coli (opa)] expressed the heat-modifiable opa gene product (the Opa protein) in their outer membrane and adhered to and invaded ME-180 human endocervical epithelial cells. In a 2-h adherence assay, an average of 26.7 E. coli (opa) adhered per ME-180 cell, whereas the control E. coli carrying only the expression vector (pKT279) did not adhere at all (less than 0.15 bacterium per cell). We investigated the ability of the adherent E. coli (opa) to invade ME-180 epithelial cells by using a gentamicin selection assay. We recovered up to 1 x 10(6) gentamicin-resistant bacteria per monolayer when ME-180 cells were infected with E. coli (opa) compared to less than 10 bacteria when the epithelial cells were infected with the same number of control E. coli (pKT279). The kinetics and level of invasion by E. coli (opa) were similar to invasion by Opa+ N. gonorrhoeae. Maximum invasion occurred 4 h after infection with 4 x 10(7) bacteria. Transmission electron microscopy studies confirmed that E. coli (opa) invaded ME-180 cells. In comparative studies, the number of E. coli (opa) that invaded HEC-1-B human endometrial epithelial cells was about an order of magnitude less than the number that invaded ME-180 cells, and E. coli (opa) did not invade Chang human conjunctival epithelial cells at all. The observations that early (less than 4 h) invasion by E. coli (opa) was dramatically inhibited, in a dose-responsive manner, by the actin-disrupting reagent cytochalasin D but later invasion (8-24 h) was not suggest that invasion mediated by Opa proteins may occur by two mechanisms, only one of which is dependent upon microfilament function. Transmission electron microscopy also revealed that infected epithelial cells had a dramatically increased amount of cytoplasmic fibrillar material surrounding the nucleus. The function and genesis of this material remain unclear. These studies indicate that at least one gonococcal Opa protein is an invasin.

Anaerobic growth of gonococci does not alter their Opa-mediated interactions with human neutrophils

Gonococci grown anaerobically (anaerobic gonococci) in the presence of nitrite induce the expression of at least three novel outer membrane proteins (PANs 1 to 3). Although PAN 1 is expressed by gonococci during gonorrhea, the function of the PAN proteins remains unknown. In the absence of serum, gonococci possessing opacity-associated (Opa, formerly PII) outer membrane proteins adhere to, stimulate, and are phagocytically killed by human neutrophils. Gonococci lacking Opa proteins demonstrate none of these activities. We investigated whether the PAN proteins, or any other characteristics of anaerobic gonococci, altered the ability of nonpiliated, Opa+ or Opa- gonococci to adhere to, stimulate, or be phagocytically killed by neutrophils. The expression of Opa4 by strain F62, as determined by its relative mobility on sodium dodecyl sulfate-polyacrylamide gels, appeared to be unaltered by anaerobic growth, as seen previously (V. L. Clark, L. A. Campbell, D. A. Palermo, T. M. Evans, and K. W. Klimpel, Infect Immun. 55:1359-1364, 1987). Anaerobic and aerobic Opa+ gonococci adhered to and stimulated neutrophils to the same extent. Similarly, anaerobic and aerobic Opa- gonococci adhered to and stimulated neutrophils equally poorly. Finally, anaerobic and aerobic Opa+ gonococci were equally sensitive to phagocytic killing by neutrophils, while anaerobic and aerobic Opa- gonococci were equally resistant to killing. Thus, the role of Opa proteins in mediating the interactions of gonococci with human neutrophils appears unaltered by anaerobic growth, and the PAN proteins, or other cryptic properties of anaerobic gonococci, do not seem to modulate or mediate these phenomena.

Growth of Neisseria gonorrhoeae in CMP-N-acetylneuraminic acid inhibits nonopsonic (opacity-associated outer membrane protein-mediated) interactions with human neutrophils

Gonococci possessing certain opacity-associated (Opa) outer membrane proteins adhere to and are phagocytosed by human neutrophils in the absence of serum. Recently, it has been shown that serum-sensitive strains of Neisseria gonorrhoeae possessing the appropriate lipooligosaccharide phenotype become serum resistant when grown in the presence of CMP-N-acetylneuraminic acid (CMP-NANA) because of sialylation of their lipooligosaccharide. We investigated whether such sialylation affects nonopsonic (antibody- and complement-independent) interactions of gonococci with human neutrophils in vitro. We grew Opa+ gonococci in the presence of up to 50 micrograms of CMP-NANA per ml, incubated them with neutrophils in vitro, and measured their abilities to adhere to neutrophils, stimulate neutrophil luminol-dependent chemiluminescence (LDCL), and be phagocytically killed by neutrophils. Growth in CMP-NANA dramatically inhibited (in a dose-dependent manner) the ability of Opa+ gonococci to adhere to neutrophils and stimulate neutrophil LDCL. Growth of Opa+ gonococci in 50 micrograms of CMP-NANA per ml appeared to delay, but did not inhibit, their killing by neutrophils. Sialidase treatment of sialylated Opa+ gonococci, i.e., gonococci grown with CMP-NANA, totally restored their abilities to adhere to neutrophils and stimulate neutrophil LDCL. Opa- gonococci grown in the presence of 50 micrograms of CMP-NANA per ml and opsonized with fresh human serum bound to neutrophils only about 30% less efficiently than did Opa- gonococci grown without CMP-NANA and opsonized. The results of our studies show that sialylated Opa+ gonococci have dramatically reduced nonopsonic interactions with neutrophils. Some gonococcal strains may resist killing by human neutrophils in vivo by such a mechanism.

Stimulation of human neutrophil oxidative metabolism by nonopsonized Neisseria gonorrhoeae

Nonopsonized gonococci possessing opacity-associated (Opa; previously PII) outer membrane proteins stimulate neutrophils to undergo a vigorous oxidative response when measured by luminol-dependent chemiluminescence (LDCL). In these studies, we characterized the mechanism of this stimulation. No gonococci that we tested induced measurable release of neutrophil superoxide anion (O2-) or hydrogen peroxide (H2O2) as measured by reduction of cytochrome c or the oxidation of scopoletin, respectively. Neutrophils pretreated with gonococci and then exposed to phorbol myristate acetate, the chemotactic peptide formylmethionylleucylphenylalanine, or opsonized zymosan released levels of neutrophil O2- and H2O2 comparable to controls, indicating that gonococci were not preventing or inhibiting neutrophil O2- or H2O2 release. To ascertain a possible explanation for these seemingly contradictory observations (i.e., induction of LDCL, but no release of O2- or H2O2), we further characterized the ability of Opa+ gonococci to stimulate LDCL. By using 1 mM azide and 4 U of horseradish peroxidase to monitor extracellular LDCL selectively and 2,000 U of catalase to monitor intracellular LDCL selectively, we determined that greater than 80% of total gonococcus-induced neutrophil LDCL occurred intracellularly. In addition, neutrophils stimulated with Opa+ gonococci showed a marked increase in O2 uptake and hexose monophosphate shunt activity. We conclude that Neisseria gonorrhoeae induces neutrophil oxidative metabolism without causing release of detectable amounts of reactive oxygen intermediates into the surrounding milieu. The gonococcus apparently directs oxidase assembly and activity to the phagolysosomal membrane. This could be a mechanism by which extracellular gonococci persist for extended periods in vivo in the presence of high concentrations of neutrophils.

Prevalence of gene sequences coding for hypervariable regions of Opa (protein II) in Neisseria gonorrhoeae

Opas (protein IIs) are a family of surface-exposed proteins of Neisseria gonorrhoeae. Each strain of N. gonorrhoeae has multiple (10-11) genes encoding for Opas. Identifiable elements in opa genes include the coding repeat within the signal sequence, conserve 5' and 3' regions, and hypervariable regions (HV1 and HV2) located within the structural gene. N. gonorrhoeae strains appear to have many biological properties in common that are either HV-region-mediated or associated with the presence of specific HV regions, suggesting that HV regions could be found in many clinical isolates. Oligonucleotides from three source strains representing three conserved regions of opa, 12 HV1 regions, and 14 HV2 regions were used by dot blot analysis to probe 120 clinical isolates of N. gonorrhoeae. The probe for the coding repeat hybridized to all 120 strains, the 3' conserved-region probe reacted with 98% of the strains, and the 5' conserved-region probe with 90% of the strains. Nine HV1 probes hybridized to 3.3-39.2% of the strains, and 13 of the HV2 probes hybridized to 1.7-25% of the isolates. Analysis of the number of probes that hybridized to each of the isolates showed that 19% did not hybridize with any of the HV1 probes and 25% did not hybridize with any of the HV2 probes. Approximately three-quarters of the isolates hybridized with one, two or three of the HV1 probes or one, two or three of the HV2 probes; 89% of the isolates hybridized to least one HV1 or one HV2 probe. The data indicate that some genes encoding HV regions of N. gonorrhoeae Opa proteins are widely distributed in nature.

Interactions of Neisseria gonorrhoeae with human neutrophils: studies with purified PII (Opa) outer membrane proteins and synthetic Opa peptides

We investigated the role of gonococcal outer membrane protein PII (also called Opa protein) in nonopsonic adherence to human neutrophils. Gonococcal outer membranes, purified Opa in detergent (Opa), purified Opa in liposomes (Opa+ lips), and peptides composing the second hypervariable (HV2) region of OpaB (strain FA1090) in liposomes (pepHV2 lips) were tested for their abilities to inhibit subsequent gonococcal adherence to human neutrophils. Outer membranes from gonococci possessing adherent Opa, liposomes containing adherent Opa, purified adherent Opa, and two of three liposome preparations (pepHV2 lips) containing peptides from the HV2 region of an adherent Opa inhibited subsequent adherence to neutrophils of homologous Opa+ gonococci. On the other hand, outer membranes from Opa- gonococci, outer membranes containing a nonadherent Opa (OpaA from strain FA1090), purified OpaA, and OpaA lips had little or no inhibitory effect. Outer membranes containing adherent Opas, purified adherent Opas, and liposomes containing such Opas all bound to neutrophils, whereas preparations containing OpaA or no Opa protein did not. The results indicate that (i) Opa proteins can bind to neutrophils in a partially purified or purified form and (ii) the HV2 region of Opa appears to at least partially mediate Opa's biological role.

Up-regulation of human neutrophil receptors for Neisseria gonorrhoeae expressing PII outer membrane proteins

In the absence of serum, nonpiliated gonococci expressing PII outer membrane proteins (PIIs) adhere to human neutrophils whereas non-PII-expressing (PII-) gonococci do not. After an observation that neutrophils in monolayers bound more gonococci than neutrophils in suspension, we treated neutrophil suspensions with known stimulants of degranulation and measured subsequent gonococcal adherence to suspended neutrophils. The chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (fmlp), the potent secretagogue phorbol myristate acetate, and the calcium ionophore A23187 all caused increased adherence of PII+ gonococci, but not PII- gonococci, to neutrophils in a dose-responsive manner. Increased adherence of gonococci to neutrophils was paralleled by increased degranulation of neutrophil myeloperoxidase, lysozyme, and lactoferrin. Inhibition of fmlp-induced neutrophil degranulation by pertussis toxin, the calmodulin inhibitors trifluoperazine and N-5-chloronaphthalene sulfonamide, or the intracellular calcium-binding agent trimethoxybenzoic acid also inhibited fmlp-induced gonococcal adherence to neutrophils. Neither undifferentiated nor myelocytically differentiated HL-60 cells, which possess primary but defective or nonexistent secondary granules, bound PII+ or PII- gonococci. Gonococci did not adhere to human monocytes, monocyte-derived macrophages, lymphocytes, platelets, or erythrocytes, indicating that several receptors, such as the complement receptors CR1, CR3 (CD11b/CD18), and CR4 (CD11c/CD18) or the adherence complex LFA-1 (CD11a/CD18), were probably not involved in gonococcal adherence to human neutrophils.

Opa (protein II) influences gonococcal organization in colonies, surface appearance, size and attachment to human fallopian tube tissues

Opa-expressing variants of Neisseria gonorrhoeae strain F62-SF and an Opa- variant, all non-piliated, were examined for differences in the interaction of the bacteria within colonies and in attachment to and damage of human fallopian tube mucosa. Expression of certain Opas was associated with the formation of transparent colonies where the bacteria were tightly packed and evenly spaced within the colonies. Expression of other Opas was associated with the formation of opaque colonies where the gonococci were less tightly packed and were unevenly spaced. Distinct differences in the size of the gonococci and in their surface characteristics were dependent upon the Opa being expressed. Certain Opas were associated with gonococci that had significantly larger cross-sectional areas and bigger perimeters. Scanning electron microscopy showed that OpaC- and OpaD-containing variants yielded greater mucosal damage than OpaB-containing and Opa- variants with the least damage caused by the OpaA-containing variant (clumped bacteria from dark opaque friable colonies). The mucosal damage after 60 min incubation included shortening and decreased numbers of microvilli on non-ciliated cells and invagination and sloughing of ciliated cells. Differences in the interactions of gonococci within colonies and in attachment to fallopian tube mucosa and damage to the mucosal cells occurred with different Opa-expressing variants of N. gonorrhoeae strain F62-SF.

Monoclonal antibodies to outer membrane protein PII block interactions of Neisseria gonorrhoeae with human neutrophils

Nonopsonic binding of gonococci to human neutrophils appears to be mediated by a family of heat-modifiable outer membrane proteins termed protein IIs (PIIs). We studied the ability of a wide variety of antigonococcal monoclonal antibodies (MAbs) to inhibit the interactions of nonpiliated PII+ gonococci with human neutrophils by measuring gonococcal adherence to neutrophils and subsequent luminol-enhanced neutrophil chemiluminescence. From one set of 95 MAbs reacting with whole gonococci, only two, 7VA2 and 7B9, inhibited the ability of gonococci to induce neutrophil chemiluminescence. 7VA2 and 7B9 both reacted only with PII. MAb 53C4, from a smaller set of anti-PII MAbs, inhibited adherence to neutrophils of PII variants that bound 53C4, but not of PII variants that did not. It also inhibited gonococcus-induced neutrophil chemiluminescence. Using a whole-cell binding assay and Western blotting (immunoblotting), we showed that MAb 53C4 bound to one PII (PII4) of strain F62 and to two PIIs (PIIb and PIId) of strain FA1090. The present studies confirm and extend the role of PII in gonococcal adherence to and stimulation of human neutrophils and show intrastrain conservation of PII epitopes. The results indicate that PII is the only outer membrane component involved in adherence of nonpiliated gonococci to human neutrophils.

Interaction of non-piliated Neisseria gonorrhoeae strain 7122 and protein IA with an epithelial cell monolayer

Studies with [14C] uracil-labelled bacteria revealed that the interaction of Neisseria gonorrhoeae with epithelial cells occurred in a time-dependent reaction which is slightly pH-dependent and optimal at pH 6.5. Immunofluorescence tests and immunoelectron microscopy of ultrathin sections confirmed the attachment of these bacteria to the epithelial cell membrane. The interaction of purified protein I with epithelial cells was time-dependent and reached equilibrium after four hours as shown by tracer experiments with 125I-labeled protein I. Cleavage experiments with trypsin followed by SDS-PAGE and autoradiography indicated that protein I (labeled with 125I) was associated with the membrane of the epithelial cells and only partly accessible by trypsin after its interaction with these mammalian cells. Immunofluorescence tests as well as immunoelectron microscopy with the monoclonal antibody G7A2C and gold-labeled protein A confirmed a dense association pattern of protein I with the cell monolayer.

Impairment of phagocytosis by the Klebsiella pneumoniae mannose-inhibitable adhesin-T7 receptor

It has been previously shown that Klebsiella pneumoniae K59 carrying the mannose-inhibitable adhesin-T7 receptor (MIAT) efficiently binds to polymorphonuclear leukocytes (PMNs) incubated at 4 degrees C but is not efficiently bound and internalized by phagocytes incubated at 37 degrees C. Pretreatment of K59 with compounds that bind the MIAT ligand (D-mannose, UV-inactivated T7 phages, and pepsin-digested anti-MIAT antibodies) enables PMNs to phagocytize and kill these bacteria. In this article, we show that the incubation temperature has no direct effect on expression of either the MIAT or the PMN receptors. These receptors were always expressed at 37 degrees C when PMNs were treated with substances that impaired their ability to rearrange their surfaces (glutaraldehyde and cytochalasins B and D). Pretreatment of inert PMNs with concanavalin A or succinyl concanavalin A drastically reduced binding of K59 to phagocytes at both 4 and 37 degrees C. The same pretreatment carried out with metabolically active PMNs enabled them to efficiently phagocytize the MIAT-positive strain. When phagocytes were treated with K59 bacteria, they became unable to ingest and kill a K59 mutant not expressing the MIAT which was sensitive to phagocytosis. If this pretreatment was performed in the presence of D-mannose, UV-inactivated T7 phages, and pepsin-digested anti-MIAT antibodies, PMNs maintained their phagocytic activity against the MIAT-negative strain. In the presence of K59 bacteria, a very low chemiluminescence response was generated; in contrast, a significant response was observed when bacteria were previously absorbed with UV-inactivated T7 phages and pepsin-digested anti-MIAT antibodies. These results support our previous suggestion that the MIAT adhesin triggers changes in the cell surface, inhibiting further binding and phagocytosis.

Energy is required for maximal adherence of Neisseria gonorrhoeae to phagocytic and nonphagocytic cells

The possibility that gonococcal energy might play a role in the interaction of Neisseria gonorrhoeae with both phagocytic and nonphagocytic cells was examined. Respiratory chain inhibitors including KCN and amobarbital resulted in reduction in gonococcal association with human neutrophils. Similar results were seen with HeLa cells and the human promyelocytic (HL-60) cell line. Identical conditions did not affect the opsonin-dependent association of Staphylococcus aureus with the same cell types. New protein synthesis by gonococci did not account for the observed reduction in association. These results suggest that energy is needed for maximal opsonin-independent association of gonococci with mammalian cells.

Gonococci possessing only certain P.II outer membrane proteins interact with human neutrophils

We investigated the role of the protein II (P.II) family of gonococcal outer membrane proteins in the interaction of seven single P.II variants of Neisseria gonorrhoeae FA1090 with human neutrophils in vitro. The abilities of nonpiliated gonococci to adhere to and be killed by neutrophils and to stimulate luminol-dependent chemiluminescence (CL) depended on the possession of at least one P.II. Gonococci lacking P.II (i.e., P.II-) adhered poorly to and were not killed by neutrophils and induced only minimal CL. Although most P.II-containing (i.e., P.II+) variants adhered to, stimulated, and were readily killed by neutrophils, one variant, containing P.IIa, possessed none of these characteristics; it acted just like a P.II- variant. No correlation was found between the colony opacity phenotype and the interaction of gonococci with neutrophils. Data from CL experiments suggest that the stimulatory effect of P.II was dominant over that of pili; i.e., piliated P.II+ gonococci were much more stimulatory than piliated P.II- gonococci. The results indicate that most but not all P.II proteins mediate, in part or in full, the interaction of N. gonorrhoeae with human neutrophils, including adherence, stimulation of the neutrophil respiratory burst, and phagocytic killing.

Chemical characterization of binding properties of opacity-associated protein II from Neisseria gonorrhoeae

Binding of an opacity-associated protein II (PIIop) from Neisseria gonorrhoeae to eucaryotic macromolecules was studied. HeLa cell extracts were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis and transferred to nitrocellulose, and purified PIIop bound to approximately 50 distinct molecular species. The binding of PIIop to HeLa cell components was stable in high salt and nonionic detergent and was not inhibited by a variety of monosaccharides and polyionic substances. PIIop binding behavior was compared with that of two model carbohydrate-binding proteins, wheat germ agglutinin (WGA) and concanavalin A (ConA). Model glycoproteins (ovomucoid, fetuin, mucin, ovalbumin) inhibited binding by PIIop, WGA, and ConA to various degrees. HeLa cell glycopeptides, generated by pronase digestion of chloroform-methanol-extracted cells, were tested for their ability to inhibit binding by PIIop to Western blots of HeLa cell macromolecules. HeLa cell extracts inhibited PIIop binding before pronase treatment, but inhibitory activity was lost as a result of pronase digestion. Direct binding to defined glycosylated and nonglycosylated proteins revealed that ConA and WGA bound only glycoproteins, whereas PIIop bound to proteins lacking carbohydrate as well. PIIop binding to human and bovine serum albumins was of high affinity and required partial unfolding of albumin; native albumin was not bound by PIIop; however, both the denatured, reduced form of albumin and the compact, nonreduced form of carboxymethylated albumin were bound strongly by PIIop. Albumin-PIIop interaction did not involve covalent bond formation through sulfhydryl groups. The predominant binding interactions of PIIop found in this study were with protein rather than carbohydrate, and the chemical nature of the interactions is more complex than involvement of purely ionic or hydrophobic forces.

Stimulation of human leukocytes by protein II+ gonococci is mediated by lectin-like gonococcal components

We investigated the ability of carbohydrates, glycosidases, and concanavalin A to inhibit the stimulation of the human leukocyte oxidative burst by gonococci in the absence of serum. The gonococci used in this study contained protein II (P.II) outer membrane proteins, and neutrophil oxidative burst was measured by luminol-enhanced chemiluminescence (CL). The following carbohydrates inhibited CL induced by nonpiliated P.II+ gonococci: beta-D-glucosamine greater than N-acetylneuraminic acid (sialic acid) greater than mannose greater than alpha-methylmannoside greater than N-acetyl-beta-D-glucosamine greater than or equal to glucose greater than or equal to lactose. Fucose, galactose, or beta-D-galactosamine (all 100 mM) did not inhibit or slightly increased CL, indicating a specificity for the observed effects. Mannose and alpha-methylmannoside also inhibited induction of monocyte CL by P.II+ gonococci. Incubation of neutrophils with concanavalin A inhibited subsequent gonococcus-induced CL but not phorbol myristate acetate-induced CL. Treatment of neutrophils with alpha-mannosidase reduced subsequent gonococcus-induced CL greater than 99%, whereas such treatment of gonococci had no effect on their ability to induce neutrophil CL. Incubation of a P.IIb-containing variant of Neisseria gonorrhoeae FA1090 with anti-P.IIb monoclonal antibody inhibited subsequent stimulation of neutrophil CL in a dose-responsive manner, indicating a specific role for P.IIb in the stimulatory process. The data suggest that one or more lectin-like components on the surface of P.II+ gonococci mediate their ability to stimulate the oxidative burst of human phagocytes.

Purification and antigenic relatedness of proteins II of Neisseria gonorrhoeae

Gonococcal proteins II from three strains were purified by chromatofocusing, and antisera was raised against them. These antisera were examined by immunoblotting to explore the antigenic relatedness of proteins II of seven different strains. The strongest reactions of the antisera were with the homologous proteins II. The antiserum against the proteins II of one strain also reacted with the proteins II present in all of the heterologous strains, whereas the antisera against the proteins II of two other strains showed little cross-reactivity with heterologous proteins II. Monoclonal antibodies produced against the three proteins II of strain F62 were specific for homologous proteins II and recognized epitopes unique to each individual protein II. These studies confirm the extensive intra- and interstrain variability in the antigenic structure of these proteins.

Role of anti-pilus antibodies in host defense against gonococcal infection studied with monoclonal anti-pilus antibodies

Several monoclonal antibodies directed against gonococcal pili have been used to investigate the potential contribution of anti-pilus antibodies to host defense against gonococcal infection. Included were two antibodies (SM1 and SM2) which reacted with conserved determinants present on pili from all strains tested and others which exhibited antigenic specificity. Immunoblotting experiments revealed that antibodies SM1 and SM2 recognize epitopes on two different peptides derived by CNBr cleavage of alpha-pili from Neisseria gonorrhoeae P9-2. All antibodies used were capable of activating complement, as shown by their ability to bind Clq, and one type-specific antibody was effective in complement-mediated bactericidal killing. Antibodies directed against at least some pilus epitopes may therefore contribute to bactericidal activity during the course of natural infection. The opsonic effect of type-specific antibodies was demonstrated by their ability to stimulate luminol-dependent chemiluminescence of human polymorphonuclear leukocytes and promote phagocytic killing of variant P9-2. Phagocytic killing in the presence of each monoclonal antibody paralleled the increase in chemiluminescence, suggesting that for this variant killing was an inevitable consequence of the interaction of polymorphonuclear leukocytes with gonococci opsonized with anti-pilus antibodies. Antibody-mediated chemiluminescence of polymorphonuclear leukocytes was enhanced in the presence of human complement, and a weak opsonic effect was detected with one of the cross-reacting antibodies (SM1) when this system was used. Although cross-reacting antibody SM1 and type-specific antibody SM13 showed considerable differences in biological properties, they were of the same isotype and bound to native pili on intact gonococci in similar numbers and with similar avidity.

Surface characteristics of group A streptococci with and without M-protein

Twenty M protein-positive and eight M protein-negative strains of group A streptococci were investigated with respect to surface hydrophobicity and amount of lipoteichoic acid (LTA). Surface hydrophobicity as determined in polymer two-phase systems varied substantially between individual strains and there was no correlation to the presence of antiphagocytic M protein. The amount of LTA on the surface of the bacteria varied with hydrophobic affinity of the cells. Strains with a high content of surface LTA were found among both M-positive and M-negative streptococci. Cellular and extracellular LTA was estimated on six strains by the ability of hot phenol extracts and culture fluids to sensitize erythrocytes and by rocket immunoelectrophoretic quantitation. Differences in content of surface LTA did not correlate to differences in the total amount of cellular LTA. Pepsin digestion of M-positive group A streptococci at suboptimal pH resulted in a loss of M antigen whereas surface LTA and the hydrophobic interaction liability was retained. The results indicate that the degree of surface hydrophobicity as measured by two-phase partitioning is not correlated to either the type-specific or the antiphagocytic moiety of M protein. The results support the correlation between surface LTA and surface hydrophobicity of group A streptococci.

Inhibition of Neisseria gonorrhoeae attachment to HeLa cells with monoclonal antibody directed against a protein II

This study showed that a protein II (PII) of Neisseria gonorrhoeae FA1090 appeared to act as a mediator of attachment to HeLa cells. Two colony variants of FA1090 were selected. Both gonococcal variants were nonpiliated, but one contained a PII and the other did not. A monoclonal antibody (1090-10.1), which was directed against the PII, inhibited the apparent PII-mediated attachment to HeLa cells. Antibodies produced from clone 1035-4, which had no PII specificity, did not inhibit the attachment and were used as controls. Inhibition of gonococcal attachment by the 1090-10.1 monoclonal antibodies was demonstrated by fluorescent microscopy analysis. Monoclonal antibody 1090-10.1 appeared to cause agglutination of the PII-containing organism. To block the clumping caused by the PII-specific monoclonal antibodies, Fab fragments of goat anti-mouse IgG were incubated with gonococci and the 1090-10.1 monoclonal antibodies. The results showed that the goat anti-mouse IgG Fab fragments partially blocked the agglutination caused by the PII-specific monoclonal antibody. The effect of the 1090-10.1 antibodies on attachment was also determined by monitoring the HeLa cells with attached iodinated gonococci. The monoclonal antibody appeared to inhibit the PII-mediated attachment.

Laboratory and wild-type Klebsiella pneumoniae strains carrying mannose-inhibitable adhesins and receptors for coliphages T3 and T7 are more pathogenic for mice than are strains without such receptors

We have shown previously that Klebsiella pneumoniae receptors for coliphages T3 and T7 also mediate mannose-inhibitable adherence to human epithelial cells and protect bacteria from phagocytosis and intracellular killing by human polymorphonuclear cells. In this paper we analyze the possible role of such mannose-inhibitable adhesins and T3-T7 receptors (MIAT) in K. pneumoniae intraperitoneal pathogenicity for mice. We showed that intraperitoneal pathogenicity for mice of four different Klebsiella strains (one laboratory and three wild-type) that carry the MIAT was approximately 60-fold higher than that of four derivative strains that lost such receptors by spontaneous mutation. The MIAT could be repressed by Klebsiella phage AP3 lysogenic conversion. Two laboratory and two wild-type strains converted by phage AP3 were also approximately 60-fold less pathogenic for mice than parental strains and showed a pathogenicity level equal to that of the MIAT-negative mutants. Studies of protection in mice with anti-whole cell antisera showed that passive immunization against MIAT-positive cells was more protective than immunization against MIAT-negative cells. Studies of protection in mice by both active and passive immunization with lipopolysaccharide and purified outer membrane proteins have shown that the proteins are the most protective outer membrane components. Since it has been shown previously that the Klebsiella receptors for T3-T7 have a proteic component and that an outer membrane protein is missing in the strains resistant to T3-T7 (C. Pruzzo et al., in R. C. Berkely (ed.), Microbial Adhesion to Surfaces, 1980); the latter finding further supports the role of MIAT in the pathogenicity of Klebsiella for mice.

Mannose-inhibitable adhesins and T3-T7 receptors of Klebsiella pneumoniae inhibit phagocytosis and intracellular killing by human polymorphonuclear leukocytes

It has recently been shown that Klebsiella pneumoniae strains adhere to human epithelial cells and that adherence is mediated by mannose-inhibitable adhesins which are also receptors for coliphages T3 and T7. We have now found that Klebsiella strain K59, which adheres to human epithelial cells and carries the receptors for coliphages T3 and T7, adheres to human polymorphonuclear leukocytes (PMN) at 4 degrees C. Strains KRTT1 and KRTT2, which are spontaneous mutants unable to adsorb coliphages T3 and T7 and adhere to human epithelial cells, at this temperature did not adhere to PMN. Adherence of K59 cells to PMN at 4 degrees C was inhibited by D-mannose, by UV-inactivated T7 phages, and by pepsin-digested anti-K59 antibodies absorbed with KRTT1 cells. At 37 degrees C the number of PMN with KRTT bacteria associated was fourfold higher than at 4 degrees C. On the contrary, the number of PMN with K59 bacteria associated at this temperature was fourfold lower than at 4 degrees C. Phagocytosis and intracellular killing experiments performed at 37 degrees C showed that KRTT1 and KRTT2 were phagocytized and killed at a higher rate than K59. After blocking of the mannose-inhibitable adhesins and T3-T7 receptors (MIAT) by D-mannose, UV-inactivated bacteriophage T7, or specific antibodies, K59 cells became more sensitive to phagocytosis and intracellular killing at 37 degrees C. K59 cells lysogenic for prophage AP3 were approximately as sensitive to phagocytosis and intracellular killing by human PMN as strains KRTT1 and KRTT2. Unencapsulated Klebsiella strains isolated from clinical specimens were found to carry MIAT most often. Four such strains were found much more resistant to phagocytosis and intracellular killing than their spontaneous mutants resistant to bacteriophages T3 and T7.

Interactions of Neisseria gonorrhoeae with human neutrophils: effects of serum and gonococcal opacity on phagocyte killing and chemiluminescence

Serum-sensitive strains of Neisseria gonorrhoeae were incubated with suspensions of normal or chronic granulomatous disease human neutrophils in the absence or presence of fresh or heat-inactivated human serum; phagocytosis, gonococcal viability, and chemiluminescence were measured. Nonpiliated opaque or transparent gonococci (colony types 3 and 4, respectively) were used for phagocytic bactericidal assays. In the presence of 2.0% fresh human serum, normal neutrophils killed >90% of types 3 and 4 gonococci by 135 min. Serum alone at this concentration was not bactericidal. In the absence of serum, type 4 gonococci were not killed, whereas type 3 gonococci were killed to the same degree as in the presence of serum. Interestingly, heat-inactivated normal serum slightly inhibited phagocytic killing of type 3 gonococci. Results almost identical to those above were obtained when 5% fresh human serum deficient in complement component 7 was substituted for 2% normal autologous serum. This indicated that the later components of complement were not involved in the observed results. To investigate the mechanisms responsible for the intracellular killing of the gonococci, we used neutrophils from patients with chronic granulomatous disease. These neutrophils are deficient in an activable NADPH oxidase and do not produce bactericidal oxygen products upon phagocytic stimulation. Neutrophils from two unrelated boys with chronic granulomatous disease killed type 3 and 4 gonococci to the same degree as did normal neutrophils. As with normal neutrophils, serum was needed for killing type 4 organisms. As expected, neutrophils from these patients showed absolutely no increased chemiluminescence in the presence of type 3 or 4 gonococci, with or without serum. The effects of serum on gonococcus-induced chemiluminescence by normal neutrophils was also investigated. For these studies, in addition to type 3 and 4 gonococci, we also used transparent colony types of lightly (type 1) and heavily (type 2) piliated organisms. Chemiluminescence induced by type 1, 2, or 3 gonococci (i.e., gonococci possessing either pili or opacity-associated proteins, but not both) was augmented only slightly by serum and then only at low ratios of gonococci to neutrophils. On the other hand, chemiluminescence induced by type 4 gonococci (i.e., gonococci possessing neither pili nor opacity-associated proteins) was substantially increased in the presence of serum. Stimulation of chemiluminescence by type 1, 2, 3, or 4 gonococci was dose dependent in the absence or presence of serum. Heat-killed type 3 gonococci induced chemiluminescence to the same degree as did viable organisms. Since the gonococci used in this research was strongly catalase positive, as are gonococci in general, and since it was killed by chronic granulomatous disease neutrophils, the results indicate that gonococci can be effectively killed within neutrophils, i.e., within phagolysosomes, by nonoxidative bactericidal mechanisms. Whereas type 3 gonococci were phagocytized and killed by neutrophils equally well with or without serum, serum was obligatory for phagocytic killing of type 4 gonococci, i.e., gonococci lacking opacity-associated proteins. In addition, either pili or opacity-associated proteins were apparently necessary for maximal stimulation of neutrophil chemiluminescence. The submaximal stimulation of chemiluminescence by gonococci lacking both pili and opacity-associated proteins, i.e., type 4 gonococci was augmented by low concentrations of nonimmune serum.

Proteinaceous bacterial adhesins and their receptors

The adhesion of bacteria to surfaces is an ecologically important property which enables them to colonize their natural habitats. Adhesion between bacteria mediated by sex pili and aggregation substances may also promote gene transfers. In this review, we describe the adhesive properties of bacteria (to eukaryotic and prokaryotic cells, and inert surfaces) and emphasize the characteristics of adhesins (structure, function, genetics, and morphology) and their cognate receptors on target surfaces. The physiochemical interactions between bacteria and surfaces can be described by the DLVO theory, but the interaction between bacterial adhesins and their receptor is better described as a ligand receptor interaction. The DLVO theory predicts that no physical contact can occur between bacteria and surface and, hence, predicts that adhesins must be filamentous in order to bridge the space between the two bodies and allow attachment of the bacteria. Adhesins are primarily proteinaceous, although adhesins of streptococci may involve dextrans or lipoteichoic acids. The cognate receptors for adhesins all appear to contain carbohydrates and as such as likely to be glycoconjugates with carbohydrate moieties acting as the receptor sites.

Gonococci-human polymorphonuclear leukocyte interactions: metabolic studies associated with attachment and ingestion

Utilizing monolayers of human polymorphonuclear leukocytes, optimal conditions for attachment and ingestion of Neisseria gonorrhoeae were determined. Both attachment and ingestion were optimal at 36 degrees C when a bacteria-leukocyte ratio of 100:1 was employed. After 30 min of incubation, log-phase viable type 2 gonococci were attached to 90% of leukocytes, whereas log-phase viable type 4 gonococci were ingested by 80 to 90% of cells. Respiratory inhibitors had no effect on attachment or ingestion, whereas glycolytic inhibitors blocked ingestion but did not affect attachment of gonocci to the leukocyte surface. Inhibition was dose dependent and partially reversible. The oxidative metabolism of leukocytes with gonococci attached or ingested was also examined. Attachment of log-phase type 2 gonococci stimulated a minimal increase in glucose oxidation and oxygen consumption by leukocytes in contrast to marked increases by leukocytes that had ingested viable type 4 or heat-killed typed 2 organisms. These results demonstrate that attachment of log-phase type 2 gonococci to the surface membrane does not stimulate significant leukocyte oxidative metabolism nor initiate the phagocytic process.

High-molecular-weight antigenic protein complex in the outer membrane of Neisseria gonorrhoeae

The outer membrane of Neisseria gonorrhoeae contains approximately 15 proteins, with 2 or 3 accounting for over 75% of the total protein mass. Samples of outer membrane from strain 2686 T4 analyzed by electrophoresis in 2% polyacrylamide gels revealed a band with an apparent molecular weight of 800,000. The band was protein material, as indicated by trypsin and pronase sensitivity and by L-[3H]proline incorporation. Peptidoglycan, nucleic acids, and carbohydrate were not detected in the band. Dye binding, L-[3H]proline incorporation, and labeling of solubilized outer-membrane proteins with 125I-labeled Bolton-Hunter reagent indicated that the band made up 10 to 13% of the total protein mass of isolated outer membranes. The material in the band was purified by gel filtration and, after reduction and alkylation, quantitatively recovered as subunits with an apparent molecular weight of 76,000. The protein in complex form was exposed at the cell surface, as evidenced by labeling whole cells with 125I by using a lactoperoxidase-catalyzed reaction and with CNBr-activated dextran. Rabbit serum raised against whole 2686 T4 gonococci contained antibody which reacted with the protein complex. The protein complex was detected in all gonococcal strains tested, but its presence could not be demonstrated in several other gram-negative species.