Redirecting the immune response towards immunoprotective domains of a DNABII protein resolves experimental otitis media

The chronicity and recurrence of many bacterial diseases is largely attributable to the presence of a biofilm, and eradication of these structures is confounded by an extracellular DNA-rich matrix. DNABII proteins, including integration host factor (IHF), are critical components of the matrix formed by all human pathogens tested to date. Whereas the natural adaptive immune response to IHF is against non-protective epitopes within the carboxyl-terminal region, antibodies against the DNA-binding “tips” induce biofilm collapse. We designed a “tip-chimer” immunogen to mimic the DNA-binding regions within the α-subunit and β-subunit of IHF from nontypeable Haemophilus influenzae (IHF_NTHi). Re-direction of the natural adaptive immune response toward immunoprotective domains disrupted NTHi biofilms in vitro and in an experimental model of otitis media. Our data support the rational design of a powerful therapeutic approach, and also that of a DNABII-directed vaccine antigen that would avoid augmentation of any pre-existing natural, but nonprotective, immune response.

Bacterial biofilms are characterized by the presence of a protective extracellular polymeric substance (EPS) that incorporates both eDNA and members of the DNABII family of bacterial DNA-binding proteins. Antibodies against the “tips” of these DNA binding-domains can cause biofilm collapse, but these epitopes are masked from the host adaptive immune system when bound to eDNA, making biofilm eradication difficult. Here, the team led by Lauren Bakaletz used a chimeric peptide to generate tip-specific antibodies against nontypeable Haemophilus influenzae to treat biofilms in vitro and in vivo. The “tip-chimer” contained the immunoprotective domains from the DNA-binding tips of a DNABII protein, integration host factor (IHF), expressed by nontypeable Haemophilus influenzae. The consequent antibodies disrupted H. influenzae biofilms in vitro and were used to treat a chinchilla model of experimental otitis media when inoculated directly into the middle ear, resulting in reduced bacterial load and clearance of already established mucosal biofilms. These findings suggest that redirecting the host adaptive immune response towards the immunoprotective tips of DNABII proteins could provide a strategy to eradicate biofilms caused by various pathogens that produce these proteins.

Natural antigenic differences in the functionally equivalent extracellular DNABII proteins of bacterial biofilms provide a means for targeted biofilm therapeutics

Bacteria that persist in the oral cavity exist within complex biofilm communities. A hallmark of biofilms is the presence of an extracellular polymeric substance (EPS), which consists of polysaccharides, extracellular DNA (eDNA), and proteins, including the DNABII family of proteins. The removal of DNABII proteins from a biofilm results in the loss of structural integrity of the eDNA and the collapse of the biofilm structure. We examined the role of DNABII proteins in the biofilm structure of the periodontal pathogen Porphyromonas gingivalis and the oral commensal Streptococcus gordonii. Co-aggregation with oral streptococci is thought to facilitate the establishment of P. gingivalis within the biofilm community. We demonstrate that DNABII proteins are present in the EPS of both S. gordonii and P. gingivalis biofilms, and that these biofilms can be disrupted through the addition of antisera derived against their respective DNABII proteins. We provide evidence that both eDNA and DNABII proteins are limiting in S. gordonii but not in P. gingivalis biofilms. In addition, these proteins are capable of complementing one another functionally. We also found that whereas antisera derived against most DNABII proteins are capable of binding a wide variety of DNABII proteins, the P. gingivalis DNABII proteins are antigenically distinct. The presence of DNABII proteins in the EPS of these biofilms and the antigenic uniqueness of the P. gingivalis proteins provide an opportunity to develop therapies that are targeted to remove P. gingivalis and biofilms that contain P. gingivalis from the oral cavity.

A bacterial-biofilm-induced oral osteolytic infection can be successfully treated by immuno-targeting an extracellular nucleoid-associated protein

Periodontal disease exemplifies a chronic and recurrent infection with a necessary biofilm component. Mucosal inflammation is a hallmark response of the host seen in chronic diseases, such as colitis, gingivitis, and periodontitis (and the related disorder peri-implantitis). We have taken advantage of our recently developed rat model of human peri-implantitis that recapitulates osteolysis, the requirement of biofilm formation, and the perpetuation of the bona fide disease state, to test a new therapeutic modality with two novel components. First we used hyperimmune antiserum directed against the DNABII family of proteins, now known to be a critical component of the extracellular matrix of bacterial biofilms. Second we delivered the antiserum as cargo in biodegradable microspheres to the site of the biofilm infection. We demonstrated that delivery of a single dose of anti-DNABII in poly(lactic-co-glycolic acid) (PLGA) microspheres induced significant resolution of experimental peri-implantitis, including marked reduction of inflammation. These data support the continued development of a DNABII protein-targeted therapeutic for peri-implantitis and other chronic inflammatory pathologies of the oral cavity in animals and humans.

Biofilms can be dispersed by focusing the immune system on a common family of bacterial nucleoid-associated proteins

Bacteria that cause chronic and/or recurrent diseases often rely on a biofilm lifestyle. The foundation of the biofilm structure is the extracellular polymeric substance (EPS) that acts as a barrier to both effectors of the immune system and antimicrobial agents. Recent work has highlighted extracellular DNA (eDNA) as a key component common to many pathogenic biofilms. Here, we show that the DNABII family of proteins, well known for their strong structural influences on intracellular DNA, was also critical for the integrity of the EPS matrix of biofilms that contain eDNA. In fact, antisera derived against a purified Escherichia coli DNABII family member rapidly disrupts the biofilm EPS formed by multiple human pathogens in vitro. In addition, when a member of this family of proteins was used as an immunogen in an animal model in which the bacteria had already formed a robust biofilm at the site of infection, the resultant targeted immune response strongly ameliorated this biofilm disease in vivo. Finally, this methodology to debulk the biofilm of EPS was shown to work synergistically with otherwise ineffective traditional anti-microbial approaches in vitro. We discuss the prospects for targeting DNABII family members as a potential universal strategy for treating biofilm diseases.

Transcutaneous immunization as preventative and therapeutic regimens to protect against experimental otitis media due to nontypeable Haemophilus influenzae

We have developed three nontypeable Haemophilus influenzae (NTHI) adhesin-derived immunogens that are significantly efficacious against experimental otitis media (OM) due to NTHI when delivered parenterally. We now expanded our preventative immunization strategies to include transcutaneous immunization (TCI) as a less invasive, but potentially equally efficacious, regimen to prevent OM due to NTHI. Additionally, we examined the potential of TCI as a therapeutic immunization regimen to resolve ongoing experimental OM. Preventative immunization with NTHI outer membrane protein (OMP) P5- and type IV pilus-targeted immunogens, delivered with the adjuvant LT(R192G-L211A), induced significantly earlier clearance of NTHI from the nasopharynges and middle ears of challenged chinchillas compared with receipt of immunogen or adjuvant alone. Moreover, therapeutic immunization resulted in significant resolution of established NTHI biofilms from the middle ear space of animals compared with controls. These data advocate TCI with the adhesin-directed immunogens as an efficacious regimen for prevention and resolution of experimental NTHI-induced OM.

Peptide and recombinant antigens for protection against bacterial middle ear infection

Passive immunization of chinchillas with serum specific for either LB1 or for LPD-LB1 (f)(2,1,3) prior to challenge with heterologous NTHI isolates (relative to diversity in region three of P5-fimbrin), significantly inhibited the signs and incidence of otitis media (P < or = 0.01) induced by any of the challenge isolates. The ability of these antisera to induce total eradication of NTHI from the nasopharynx was not however equivalent among challenged cohorts. The data thus suggested that while early, complete eradication of NTHI from the nasopharynx was highly protective, reduction of the bacterial load to below a critical threshold level appeared to be similarly effective. Both immunogens thus remain strong vaccine candidates.

Passive transfer of antiserum specific for immunogens derived from a nontypeable Haemophilus influenzae adhesin and lipoprotein D prevents otitis media after heterologous challenge

We recently determined that passive transfer of serum directed against a synthetic peptide called LB1 or a recombinant fusion protein immunogen [LPD-LB1(f)(2,1,3)] could prevent otitis media after challenge with a homologous nontypeable Haemophilus influenzae (NTHI) isolate. NTHI residing in the nasopharynx was rapidly cleared from this site, thus preventing it from ascending the eustachian tube and inducing otitis media in chinchillas compromised by an ongoing viral upper respiratory tract infection. While LB1 is based solely on one NTHI adhesin, the latter immunogen, LPD-LB1(f)(2,1,3), was designed to incorporate two NTHI antigens shown to play a role in the pathogenesis of otitis media; lipoprotein D (LPD) and the P5-homologous fimbrin adhesin. The design of LPD-LB1(f)(2,1,3) also accommodated for the recently demonstrated existence of three major groupings, based on amino acid sequence diversity, in the third surface-exposed region of P5-fimbrin. LPD-LB1(f)(2,1,3) was thus designed to potentially confer broader protection against challenge by diverse strains of NTHI. Chinchillas were passively immunized here with serum specific for either LB1 or for LPD-LB1(f)(2,1,3) prior to challenge with a member of all three groups of NTHI relative to diversity in region 3. The transferred serum pools were also analyzed for titer, specificity, and several functional activities. We found that both serum pools had equivalent ability to mediate C'-dependent killing and to inhibit adherence of NTHI strains to human oropharyngeal cells. When passively transferred, both serum pools significantly inhibited the signs and incidence of otitis media (P </= 0.01) induced by any of the three challenge isolates. Despite providing protection against disease, the ability of these antisera to induce total eradication of NTHI from the nasopharynx was not equivalent among NTHI groups. These data thus suggested that while early, complete eradication of NTHI from the nasopharynx was highly protective, reduction of the bacterial load to below a critical threshold level appeared to be similarly effective.

Epitope mapping of the outer membrane protein P5-homologous fimbrin adhesin of nontypeable Haemophilus influenzae

To identify potential immunodominant and/or adhesin binding domains of the outer membrane protein P5-homologous fimbrin adhesin of nontypeable Haemophilus influenzae (NTHI), three sets of synthetic peptides were synthesized and assayed in an adherence inhibition assay, by Western blotting, and in a biomolecular interaction analysis (BIA) system. The first series of 34 8- to 10-mer peptides represented the entire mature protein sequentially. The second set of four peptides (each 19 to 28 residues) represented the four predicted major surface-exposed regions (or loops) of this adhesin. The third series of seven peptides (each 27 to 34 residues) were specifically designed to map the third surface-exposed region. Data obtained by BIA indicated limited reactivity of a panel of high-titered immune chinchilla sera to the 8- to 10-mer peptides representing the mature protein, likely because these linear peptides did not represent continuous epitopes. However, several of these short peptides did inhibit adherence of multiple NTHI strains to a human respiratory epithelial cell. Overall, greatest relative reactivity in both BIA and adherence inhibition assays was demonstrated against, or shown by, peptides mapping to the third and fourth predicted surface-exposed regions of this adhesin, thereby indicating the presence of immunodominant and adhesin binding domains at these sites. Middle ear fluids sequentially recovered from a chinchilla with an ongoing NTHI-induced otitis media (OM) as well as sera from children with OM due to NTHI also reacted exclusively with peptides representing the third and fourth surface-exposed regions of the P5-fimbrin adhesin, indicating a similarity in immune recognition of this bacterial protein by these two hosts. Collectively, these data together with the previously demonstrated protective efficacy of immunogens derived from this adhesin in chinchilla models support the continued development of P5-fimbrin based vaccine components.

Protection against development of otitis media induced by nontypeable Haemophilus influenzae by both active and passive immunization in a chinchilla model of virus-bacterium superinfection

Three separate studies, two involving active-immunization regimens and one involving a passive-transfer protocol, were conducted to initially screen and ultimately more fully assess several nontypeable Haemophilus influenzae outer membrane proteins or their derivatives for their relative protective efficacy in chinchilla models of otitis media. Initial screening of these antigens (P5-fimbrin, lipoprotein D, and P6), delivered singly or in combination with either Freund's adjuvant or alum, indicated that augmented bacterial clearance from the nasopharynx, the middle ears, or both anatomical sites could be induced by parenteral immunization with P5-fimbrin combined with lipoprotein D, lipoprotein D alone, or the synthetic chimeric peptide LB1 (derived from P5-fimbrin), respectively. Data from a second study, wherein chinchillas were immunized with LB1 or lipoprotein D, each delivered with alum, again indicated that clearance of nontypeable H. influenzae could be augmented by immunization with either of these immunogens; however, when this adjuvant was used, both antibody titers in serum and efficacy were reduced. A third study was performed to investigate passive delivery of antisera directed against either LB1, lipoprotein D, nonacylated lipoprotein D, or a unique recombinant peptide designated LPD-LB1(f)2,1,3. The last three antiserum pools were generated by using the combined adjuvant of alum plus monophosphoryl lipid A. Passive transfer of sera specific for LB1 or LPD-LB1(f)2,1,3 to adenovirus-compromised chinchillas, prior to intranasal challenge with nontypeable H. influenzae, significantly reduced the severity of signs and incidence of otitis media which developed (P </= 0.001). Collectively, these data indicate the continued merit of further developing LB1 and LPD-LB1(f)2,1,3 as components of vaccines for otitis media.

Fimbria-mediated enhanced attachment of nontypeable Haemophilus influenzae to respiratory syncytial virus-infected respiratory epithelial cells

Respiratory syncytial virus (RSV) infection is known to predispose children to otitis media and sinusitis due to bacteria such as nontypeable Haemophilus influenzae (NTHI). In this study, we investigated the role of NTHI surface outer membrane protein P5-homologous fimbriae (P5-fimbriae) in attachment to RSV-exposed A549 epithelial cells. Analysis by fluorescence flow cytometry showed that a live P5-fimbriated NTHI strain (NTHIF+) attached to a higher proportion of RSV-exposed A549 cells than to control cells (mean, 68% for RSV versus 29% for control; P = 0.008), while attachment of the P5-fimbriae-deficient isogenic mutant strain (NTHIF-) was significantly lower than in control cells and rose only slightly following RSV exposure (mean, 17% for RSV versus 10% for control, P = 0.229). Attachment of NTHIF+ did not correlate with the amount of RSV antigen expressed by A549 cells. Furthermore, paraformaldehyde-fixed NTHIF+ also demonstrated an enhanced binding to RSV-exposed cells. Observations by transmission electronic microscopy showed that the mean number of bacteria attached per 100 RSV-exposed A549 cells was higher for NTHIF+ than NTHIF- (99 versus 18; P < 0.001). No intracellular bacteria were identified. UV-irradiated conditioned supernatants collected from RSV-infected A549 cultures (UV-cRSV) also enhanced the attachment of NTHIF+ to A549, suggesting the presence of a preformed soluble mediator(s) in UV-cRSV that enhances the expression of receptors for P5-fimbriae on A549 cells. In summary, RSV infection significantly enhances NTHI attachment to respiratory epithelial cells. P5-fimbria is the critical appendage of NTHI that participates in this attachment. In clinical settings, blocking of the P5-fimbria-mediated attachment of NTHIF+ by passive or active immunity may reduce the morbidity due to NTHI during RSV infection.

Blinded multiplex PCR analyses of middle ear and nasopharyngeal fluids from chinchilla models of single- and mixed-pathogen-induced otitis media

Multiplex PCR analyses for both bacterial and viral pathogens were conducted in a blinded manner on 33 archival specimens, of known culture status, procured from chinchilla models of both single- and mixed-pathogen-induced otitis media and from a pediatric patient. These specimens had been maintained at -70 degrees C for up to 6 years. Experimental specimens evaluated included middle-ear effusions, nasopharyngeal lavage fluids and middle-ear lavage fluids from animals which were immunologically naive, sham-immunized or actively immunized with nontypeable Haemophilus influenzae antigens. Sampling times used ranged from the day of bacterial or viral challenge to 42 days after challenge. Initial PCR analyses of the 33 specimens matched the traditional culture data in 24 instances (73%), correctly identifying nontypeable H. influenzae, Moraxella catarrhalis, Streptococcus pneumoniae, or adenovirus as the causative agent. A PCR-positive signal for the microbe(s) inoculated was also obtained in four animal model specimens (12%) which were culture negative. One of two culture-negative human effusions was also PCR positive. Thus, overall, results obtained by blinded PCR were 85% concordant with traditional culture methods or correctly indicated the specific pathogen introduced in four specimens that were sterile. In no instance was a false-positive signal obtained for any of the five etiologic agents being evaluated. We conclude that the multiplex PCR analyses are rapid and accurate methodologies when they are used to retrospectively evaluate diverse archival specimens of limited volume from experimental models of otitis media.

Adherence of non-typeable Haemophilus influenzae promotes reorganization of the actin cytoskeleton in human or chinchilla epithelial cells in vitro

Non-typeable Haemophilus influenzae (NTHi) are opportunistic mucosal pathogens which adhere to epithelial cells via a variety of non-specific and specific interactions. Several adhesins have been identified and while the complimentary receptor(s) for each of these adhesins has not yet been fully characterized, it is widely accepted that adherence is an absolute prerequisite for disease. Several reports have indicated that NTHi can also be internalized and reside intracellularly. For this to occur, NTHi must be taken up by mucosal epithelial cells lining the respiratory tract. We have noted, by TEM, that adherent NTHi overlie an electron dense area in the cell membrane of human epithelial cells which is associated with a localized complex assembly of cytoskeletal fibers in the eukaryotic cytoplasm. We thus examined the potential involvement of cytoskeletal actin in this phenomenon via FITC-phalloidin labeling of respiratory tract epithelial cells which had been incubated with several clinical isolates of NTHi. Strong punctate fluorescence was coincident with adherent NTHi to both human oropharyngeal and chinchilla middle ear epithelial cells. This reactivity was similar to the discrete fluorescent spots observed with enteropathogenic Escherichia coli which were adhered to HeLa cells. In contrast, none of the NTHi isolates tested induced actin polymerization in cells of endothelial origin. While the exact mechanisms involved are yet to be elucidated, our data indicated that actin nucleation was coincident with NTHi adherence.

Kinetics of the ascension of NTHi from the nasopharynx to the middle ear coincident with adenovirus-induced compromise in the chinchilla

To determine the kinetics of ascension of the eustachian tube (ET) by non-typeable Haemophilus influenzae (NTHi) in situ from the nasopharynx to the middle ear using an experimental model of otitis media (OM), we examined snap-frozen sections of chinchilla ET and middle ear mucosa for adherent bacteria over a 14 day time period. Via fluorescent- and transmission electron-microscopy, we found that NTHi preferentially adhered not to the epithelial cells but to the mucus in the ET and gradually ascended this tubal organ, reaching the middle ear approximately 10 days after intranasal inoculation of adenovirus-infected animals. The number of NTHi adherent to mucus at the pharyngeal portion of the ET increased significantly in the first 4 days after inoculation of the nares whereas the number of adherent bacteria in both the mid and tympanic portions of the ET increased more gradually over time. NTHi were not observed in the middle ear until approximately 7-10 days after inoculation of the nares which was coincident with the onset of clinical signs of OM. These data confirmed our earlier in vitro investigation which suggested that adherence to and growth within stagnant mucus within a ET compromised by adenovirus was a possible mechanism by which NTHi, resident in the nasopharynx, might gain access to the middle ear and induce OM.

Relative immunogenicity and efficacy of two synthetic chimeric peptides of fimbrin as vaccinogens against nasopharyngeal colonization by nontypeable Haemophilus influenzae in the chinchilla

The OMP P5-homologous fimbriae of nontypeable Haemophilus influenzae (NTHi) are an adhesin and a virulence factor for otitis media in chinchilla models. We synthesized two peptides (LB1 and LB2) which incorporate determinants of the fimbrial subunit co-linearly synthesized with a "promiscuous" T-cell epitope from the fusion protein of measles virus. Sera obtained from immunized rabbits and chinchillas demonstrated significant reciprocal titers against both the homologous peptide and isolated fimbrial protein. Antisera also immunolabeled native fimbriae of whole unfixed NTHi. Immunization with LB1 or fimbrin resulted in elimination of NTHi from the chinchilla nasopharynx 2-3 weeks earlier than controls, respectively.

Particulate matter in the posterior semicircular canal

The pathoetiology of benign paroxysmal positional vertigo (BPPV) is controversial. Particulate matter within the posterior semicircular canal has been identified intraoperatively in patients with BPPV but has also been reported in non-BPPV patients at the time of translabyrinthine surgery (Parnes LS, McClure JA. Free-floating endolymphatic particles: a new operative finding during posterior semicircular canal occlusion. Laryngoscope 1992;102:988-92; Schuknecht HF, Ruby RRF. Cupulolithiasis. Adv Otorhinolaryngol 1973;20: 434-43; Kveton JF, Kashgarian M. Particulate matter within the membranous labyrinth: pathologic or normal? Am J Otol 1994;15:173-6). The nature of the particulate matter remains unknown. The purpose of this study was to prospectively examine the posterior semicircular canal of patients with and without a clinical history of BPPV for the presence of particulate matter. Seventy-three patients without BPPV symptoms undergoing labyrinthine surgery (vestibular schwannoma excision or labyrinthectomy) and 26 patients with BPPV undergoing the posterior semicircular canal occlusion procedure were compared. Additionally, 70 archived temporal bones without a history of BPPV were examined microscopically for the presence of particulate matter within the lumen of the membranous labyrinth. No particles were observed intraoperatively in any of the 73 patients without a history of BPPV. Particulate matter was observed in 8 of 26 patients at the time of the posterior semicircular canal occlusion procedure for intractable BPPV. Of the 70 temporal bones examined, 31 did not show significant postmortem changes and also did not demonstrate cupulolithiasis or canalithiasis. Particulate matter from within the membranous posterior semicircular canal was removed from one patient at the time of posterior semicircular canal occlusion for intractable BPPV symptoms and was examined by scanning electron microscopy. The particulate matter appeared morphologically consistent with degenerating otoconia. These data show a statistically significant association between the presence of particles within the posterior semicircular canal in this study and the symptom complex of BPPV.

Selective adherence of non-typeable Haemophilus influenzae (NTHi) to mucus or epithelial cells in the chinchilla eustachian tube and middle ear

Frozen sections of chinchilla Eustachian tube (ET) and middle ear mucosa were incubated with either FITC-labeled non-typeable Haemophilus influenzae (NTHi) or Bordetella pertussis. The number of bacteria adherent to "roof" vs "floor" regions was compared for each of three anatomic portions of the ET and for middle ear epithelium noting whether bacteria adhered to mucus or to epithelial cells. NTHi strains adhered significantly greater to mucus in the ET lumen whereas B. pertussis preferentially adhered to epithelial cells lining the ET (P < or = 0.05). A non-fimbriated isogenic mutant of NTHi adhered significantly less to mucus than the parental isolate at all sites of the ET floor (P < or = 0.05). Isolated fimbrin protein adhered to ET mucus and blocked adherence of whole organisms. Treatment with the mucolytic agent N-acetyl-L-cysteine resulted in significantly reduced adherence of NTHi to mucus (P < or = 0.001) and eliminated the ability to detect binding of isolated fimbrin protein. N-acetyl-L-cysteine treatment did not affect adherence of either B. pertussis or NTHi to epithelial cells. These data indicated that NTHi may mediate ascension of the ET from the nasopharynx primarily via adherence to and growth in mucus overlying the floor region of the tubal lumen. The OMP P5-homologous fimbriae were shown to contribute to this binding.

Adenovirus serotype 1 does not act synergistically with Moraxella (Branhamella) catarrhalis to induce otitis media in the chinchilla

A chinchilla model of otitis media in which adenovirus compromise of the tubotympanum facilitates the subsequent induction of middle ear disease was used to investigate Moraxella (Branhamella) catarrhalis pathogenesis. Intranasally inoculated M. catarrhalis did readily colonize the nasopharynx of this host; however, despite evidence of viral infection and tubotympanal compromise, M. catarrhalis did not induce culture-positive otitis media in this model.

Immunological aspects of otitis media: present views on possibilities of immunoprophylaxis of acute otitis media in infants and children

The article reviews, based on current knowledge of immunological events affecting the middle ear, the possibilities and prospects for the prevention of otitis media (OM) by immunologic measures. While pneumococcal capsular polysaccharide vaccines proved not to be effective against infant acute otitis media (AOM), pneumococcal conjugate vaccines provide good immunogenicity even in infants, and call for trials with better prospects of clinical efficacy. The other future approaches currently under development are vaccines against nontypable Haemophilus influenzae and Branhamella catarrhalis, anti-viral immunoprophylaxis, combinations of the above alternatives, or passive immunization. Also, the use of new routes or ways of immunization are under study. Furthermore, the ways to modify the present treatment practices of AOM to favour good immunologic responses in infants and children must be studied.

Effect of salicylate on expression of flagella by Escherichia coli and Proteus, Providencia, and Pseudomonas spp

Osmotic stress, salicylate, and Mar (multiple antibiotic resistance) mutation are known to block the expression of the OmpF porin. Since these conditions have also been shown to inhibit the expression of P and CFA fimbriae in Escherichia coli, we speculated that they might affect the expression of flagella as well. Hyperosmotic conditions have been shown to block the synthesis of flagellin and expression of flagella in E. coli (C. Li, C. J. Louise, W. Shi, and J. Adler, J. Bacteriol. 175:2229-2235, 1993). In the current study, sodium salicylate was found to inhibit the motility of E. coli, Proteus mirabilis, Proteus vulgaris, Providencia rettgeri, and Providencia stuartii in a reversible, concentration-dependent manner. Swarming did not occur at 20 mM sodium salicylate. Salicylate also blocked the synthesis of flagellin in E. coli. Phenotypic Mar mutants of E. coli derived from motile strains were amotile. Flagella were markedly reduced as determined by scanning electron microscopy when P. mirabilis was grown in broth containing 20 mM salicylate. Salicylate had no apparent effect, however, on expression of a 40-kDa porin protein in P. mirabilis. This finding suggests that the noted effect of salicylate on Proteus spp. may be mediated through a mechanism other than porin production or that the Proteus porin may not be analogous to OmpF in E. coli. Salicylate decreased the motility of Pseudomonas cepacia but had no effect on Pseudomonas aeruginosa. The exact mechanism by which salicylate exerts its effect is not known, but it appears to be related to osmoregulation.

Viral potentiation of bacterial superinfection of the respiratory tract

Virus infections of the respiratory tract predispose it to bacterial superinfections. Epidemiological studies, clinical evidence of viral-bacterial co-infection and animal models of such interactions suggest a time course of events and several mechanisms by which viral potentiation may occur. It appears that structural and functional disruption of the respiratory mucosal epithelium is a major contributor to the synergistic effects of superinfection.

Effect of endotoxin on cultured rat middle ear epithelium, rat meatal epidermis, and human keratinocytes

Several factors seem to contribute to the series of events in the pathogenesis of otitis media and cholesteatoma. Endotoxin is likely to be one of these factors, since it has been found in human middle ear effusions and since injection of this substance into the middle ear, in animal experiments, gave rise to prominent reactions. Provoking of epithelial cells in vitro with endotoxin led to distinct cell responses that might be associated with cholesteatoma formation. In this study the effect of endotoxin on serially cultured rat middle ear epithelium, rat meatal epidermis, and human keratinocytes was investigated. Endotoxin strongly stimulated the proliferation of middle ear epithelium and human keratinocytes and inhibited that of meatal epidermis. Furthermore, endotoxin affected the morphology of the three types of tissue. Rat middle ear epithelium revealed epithelial cell tracks with interconnecting bridge-like structures protruding above the culture plane, whereas rat meatal epidermis showed increased terminal differentiation expressing large areas of blister-like structures detaching from the culture dish. Cross-linked envelope analysis of human keratinocytes showed an increased terminal differentiation that was morphologically confirmed but was not confirmed by cytokeratin analysis. The results of this study support the hypothesis that endotoxin may play an important role in the pathogenesis of otitis media and cholesteatoma.

Localization of high-molecular-weight adhesion proteins of nontypeable Haemophilus influenzae by immunoelectron microscopy

A family of high-molecular-weight (HMW) surface-exposed proteins important in the attachment of nontypeable Haemophilus influenzae (NTHi) to human epithelial cells was previously identified (J. W. St. Geme III, S. Falkow, and S. J. Barenkamp, Proc. Natl. Acad. Sci. USA 90:2875-2879, 1993). In the present investigation, indirect immunogold labeling and electron microscopy were used to localize these proteins on three clinical isolates of NTHi, mutants deficient in expression of one or both HMW proteins, and embedded sections of human oropharyngeal cells after incubation with NTHi strain 12. The filamentous material comprising the proteins was labeled with monoclonal antibodies directed against two prototype HMW proteins (HMW1 and HMW2) of prototype NTHi strain 12. Gold labeling was observed as a cap or discrete aggregate off one pole or centrally along one long axis of the bacterial cell. Heavily labeled, non-bacterial-cell-associated, disk-like aggregates of the HMW proteins were frequently noted in both bacterial preparations as well as in association with the oropharyngeal cell surface and intracellularly. Mutants demonstrated diminished labeling or an absence thereof, respectively, which correlated well with their previously demonstrated reduced ability or inability to adhere to Chang conjunctival epithelial cells in vitro. The Haemophilus HMW proteins share antigenic determinants with and demonstrate amino acid sequence similarity to the filamentous hemagglutinin protein of Bordetella pertussis, a critical adhesin of that organism. The studies presented here demonstrate that the Haemophilus proteins and B. pertussis filamentous hemagglutinin show impressive morphologic and perhaps additional functional similarity.

Effect of salicylate, bismuth, osmolytes, and tetracycline resistance on expression of fimbriae by Escherichia coli

Adherence of Escherichia coli is facilitated by fimbriae and several outer membrane proteins (OMPs). Hypertonic conditions, salicylate, and Mar mutations are known to reduce OmpF expression. We speculated that OMPs involved in export or assembly of fimbrial subunits might be similarly affected. To explore this hypothesis, E. coli expressing P, type 1, S, colonization factor antigen I (CFA/I), or CFA/II fimbriae was grown in the presence of salicylate, bismuth salts, NaCl, and nonfermented sugars. Tetracycline-resistant clones were derived from several P-fimbriated strains. The bacteria were tested for the ability to agglutinate erythrocytes, yeast cells, and alpha-D-Gal(-4)-beta-D-Gal-bonded latex (Gal-Gal) beads and were examined for fimbriae by electron microscopy. Hyperosmolar conditions decreased fimbrial expression for all strains. Expression of P fimbriae by pyelonephritic strains, all of which were OmpF+, was reversibly repressed by salicylate and bismuth salts. CFA strains were similarly affected. Tetracycline-resistant P-fimbriated strains were OmpF deficient, were unable to agglutinate erythrocytes and Gal-Gal beads, and lacked fimbriae as observed by electron microscopy. Strains with plasmid-encoded P-fimbrial genes did not demonstrate OmpF on polyacrylamide gel electrophoresis profiles and were not affected by salicylate. The type 1-fimbriated phenotype was not affected by salicylate or bismuth unless the strains also expressed P fimbriae. S-fimbriated strains were not affected. The mechanism by which salicylates, bismuth salts, and tetracycline resistance inhibit or modulate the expression of P fimbriae may be mediated through OmpF and other OMPs.

Synergistic effect of adenovirus type 1 and nontypeable Haemophilus influenzae in a chinchilla model of experimental otitis media

We recently reported the development of a chinchilla model of experimental otitis media (OM) that uses a pediatric clinical isolate of adenovirus type 1 (4) and in which an active infection with the wild-type strain was demonstrated. To expand upon these findings, this study was designed to determine whether we could demonstrate adenovirus infection-induced predisposition to bacterial OM in the chinchilla, as has been shown in human epidemiological studies (D. A. Clements, F. W. Henderson, and E. C. Neebe, p. 27-29, in D. J. Lim, C. D. Bluestone, J. O. Klein, D. J. Nelson, and P. L. Ogra, ed., Proceedings of the Fifth International Symposium on Recent Advances in Otitis Media, 1993; F. W. Henderson, A. M. Collier, M. A. Sanyai, et al., N. Engl. J. Med. 306:1377-1383, 1982). In addition, we were interested in determining whether altering the order of pathogen acquisition would further affect the outcome of disease incidence and severity. Toward this end, cohorts of chinchillas were inoculated intranasally with a strain of nontypeable Haemophilus influenzae (NTHi) (86-028NP) which colonizes the chinchilla nasopharynx but does not consistently induce culture-positive OM when inoculated intranasally (L. O. Bakaletz, T. M. Hoepf, D. J. Lim, and B. Tallan, Abstr. 90th Annu. Meet. Am. Soc. Microbiol. 1990, abstr. B-66, p. 37, 1990), adenovirus type 1 and then inoculated 7 days later with NTHi, NTHi and then inoculated 7 days later with adenovirus type 1, or both pathogens concurrently. All cohorts were observed over a 35-day period and assessed for incidence and severity of OM by several methodologies. The data collectively indicated that all animals receiving both pathogens developed OM of greater severity than those receiving only a single agent. Adenovirus inoculation followed 7 days later by NTHi inoculation was the order of pathogen acquisition which induced the most prolonged presence of NTHi in both the nasopharynx and the middle ear, the most severe tympanic membrane inflammation overall, and the most significant damage to and altered function of both middle ear and eustachian tube mucosae.

Modeling adenovirus type 1-induced otitis media in the chinchilla: effect on ciliary activity and fluid transport function of eustachian tube mucosal epithelium

Previous studies have shown that viral upper respiratory tract (URT) infection predisposes to the development of bacterial otitis media (OM). The mechanisms underlying this phenomenon have been well defined for influenza A virus in the chinchilla model of experimental OM but have not been for adenovirus because of the heretofore lack of an appropriate model. In this study, chinchillas were inoculated intranasally or transbullarly with type 1 adenovirus to assess whether or not the chinchilla could serve as a suitable model for future investigation of adenovirus predisposition to bacterial OM. Data indicated that the chinchilla readily supported an active infection by and responded serologically to this agent and that route of inoculation markedly influenced otoscopic findings, elicitation of middle ear fluids, onset and location of histopathology, and progression of disease. The time course of disease onset and recovery and an assessment of the effect of this virus isolate on the mucosal epithelial integrity and on both the ciliary activity and transport function of the eustachian tube epithelium for both routes of inoculation are presented.

Effect of influenza A virus on ciliary activity and dye transport function in the chinchilla eustachian tube

Previous studies have shown that influenza A virus inoculated via a transbullar approach can cause severe disorders of the chinchilla eustachian tube. In this study, we inoculated chinchillas both intranasally and transbullarly with influenza A virus (A/Alaska/6/77) to assess the effect of this virus on both the ciliary activity of eustachian tube epithelium and eustachian tube transport function. Data indicated that while the nature of the major lesions was indistinguishable, the differing routes of inoculation did influence the time course and initial location of virus-induced histopathology. Analysis of ciliary beat frequency and dye transport function indicated a maximal decrease approximately 7 to 14 days postinoculation, with return to normal function by 28 days postinoculation. Light and transmission electron microscopic observations of the evolution of histopathology and return to normal histology correlated well with functional assessment data.

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.

Glycoconjugates in the chinchilla tubotympanum

Various biotinylated lectins were used to characterize and semiquantitate glycoconjugate residues in the tubotympanum. Epithelial goblet cells were stained predominantly by WGA, LFA, SNA, RCA-I, Con-A, LCA, SBA, PHA-E, and UEA; this finding suggests they contain alpha-neuraminic acid, beta-galactose, alpha-mannose, N-acetyl alpha-galactosamine, and alpha-fucose. Glandular mucous cells were stained predominantly by WGA, LFA, SNA, and RCA-I; this finding suggests that they contain alpha-neuraminic acid and beta-galactose. The glandular serous cells were stained predominantly by Con-A, WGA, and LFA; this finding suggests that they produced alpha-mannose and alpha-neuraminic acid that represented serum-type glycoprotein. The positive staining of epithelial goblet cells and glandular mucous cells with PNA after neuraminidase digestion suggests that they produced mucin-type glycoproteins. The staining of the mucous blanket by WGA, LFA, SNA, RCA-I, LCA, PNA, SBA, PHA-E, and UEA suggests the presence of alpha-neuraminic acid, beta-galactose, N-acetyl alpha-galactosamine, and alpha-fucose. The epithelial cell (nonsecretory) surface was stained largely by WGA, LFA, SNA, RCA-I, Con-A, and LCA; this finding suggests the presence of alpha-neuraminic acid, beta-galactose, and alpha-mannose.

Effect of vitamin A on the growth and differentiation of rat external auditory canal epithelium in organ culture

Intact rat external ear canal explants were maintained either in retinoid-deficient or retinoid-supplemented medium for 7, 10, 14, and 21 days. The morphology of the external ear canal epidermis was well maintained, including the presence of sebaceous glands even after 21 days in culture with retinoid-deficient medium. However, after culturing in retinoid-supplemented medium, the external ear canal epithelium showed both a loss of keratohyalin granules and the formation of keratin. Extensive microvilli formation occurred, even though the desquamation process continued from the superficial layer after 7, 10, and 14 days in culture with retinoid-enriched medium. After 21 days in culture with retinoid-supplemented medium, the ear canal epithelium contained well-developed Golgi apparatus and secretory granules as well. It was concluded that the ear canal epithelium was transformed into a secretory-like mucosal epithelium by retinoid supplementation.

Immunological responsiveness of chinchillas to outer membrane and isolated fimbrial proteins of nontypeable Haemophilus influenzae

Thin, nonhemagglutinating fimbriae have been demonstrated on 100% of the clinical isolates of nontypeable Haemophilus influenzae recovered from children with chronic otitis media tested in this laboratory (L. O. Bakaletz, B.M. Tallan, T.M. Hoepf, T.F. DeMaria, H.G. Birck, and D.J. Lim, Infect. Immun. 56:331-335, 1988). Chinchillas with induced otitis media responded to this surface-located antigen of both the infecting and a heterologous strain. Antibodies were found in both serum and middle ear fluids.

Effect of prostaglandin E2 and bacterial endotoxin on the rate of dye transport in the eustachian tube of the chinchilla

To determine the effects of various biologic agents on the rate of fluid transport in the eustachian tube of the chinchilla, we have established an in situ method of measuring dye transport in which the bulla remains intact. The normal rate of dye transport from an injection site in the superior bulla to the nasopharyngeal orifice of the eustachian tube was 130 +/- 10 seconds. Inhibition of ciliary activity with the local anesthetic bupivacaine resulted in a saturable delay of transport (greater than 15 minutes), while exposure to the beta-adrenergic stimulator isoproterenol caused a significant increase in transport rate (79 +/- 7 seconds). Two inflammatory mediators commonly found in chronic middle ear effusions were also tested for their effect on fluid transport by the mucociliary apparatus. Bacterial endotoxin reduced transport rates at high concentrations, while prostaglandin E2 had no effect at any concentration tested.

Effect of formalin-fixed Hemophilus influenzae and Streptococcus pneumoniae on dye transport by the chinchilla eustachian tube

An in situ method for measuring the ability of the middle ear and eustachian tube ciliated epithelium to transport dye to the nasopharynx was used to assess the role endotoxin-containing killed bacteria have on the development of otitis media with effusion. In addition, electron microscopy was used to monitor histological changes induced by exposure to these organisms and the ability of the mucosa to recover. The results indicated that exposure to a killed gram-negative but not a gram-positive otitis media pathogen leads to early production of middle ear fluid, evidence of capillary leakage and significant slowing of mucociliary transport. The damage was, however, reversible with the epithelium returning to normal both functionally and histologically within 7 days of exposure.

Beta 2-microglobulin in otitis media with effusion

beta 2-Microglobulin (beta 2M) is a low-molecular-weight protein present in serum and other fluids during various autoimmune or chronic inflammatory diseases. beta 2-Microglobulin was measured in middle ear effusion (MEE) and serum samples obtained from 36 patients with chronic otitis media with effusion. Using a quantitative competitive enzyme immunoassay, we were able to demonstrate beta 2M in 98% of the MEE samples. The mean concentration of beta 2M was higher in the MEE samples than in the serum samples. There was considerable variability between ears in those patients with bilateral MEE. There was no correlation between beta 2M concentration and the patients' age, sex, MEE type, and culture results, or cytologic profiles of the MEEs. This increased beta 2M may reflect earlier lymphocyte activity during the inflammatory process.

The effect of antecedent influenza A virus infection on the adherence of Hemophilus influenzae to chinchilla tracheal epithelium

The adherence of Hemophilus influenzae (type b and nontypable) to ciliated chinchilla respiratory epithelium was investigated using a whole organ perfusion technique. Nontypable H influenzae (NTHi) were shown to be more adherent than type b to these organized and differentiated tracheal organ cultures. Bacteria were found adhering to ciliated cells. Antecedent influenza A virus infection had no effect on adherence of NTHi for at least 48 hours. However, 72 hours after exposure to the virus, infected tissues demonstrated significantly fewer adherent bacteria than did controls. To summarize, influenza A virus infection was not found to augment the initiation of NTHi adherence to ciliated respiratory epithelium in this model.

Frequency of fimbriation of nontypable Haemophilus influenzae and its ability to adhere to chinchilla and human respiratory epithelium

To date, we have examined nearly 60 clinical isolates of nontypable Haemophilus influenzae (26 nasopharyngeal, 33 from middle ear effusions) and have found that 100% were fimbriated. The percentage of cells bearing fimbriae within each isolate varied from less than 10 to 100%, with fimbriae being either peritrichous or bipolar in distribution. Fimbriae were approximately 2.4 to 3.6 nm in width; however, there was a high degree of variability in both length and number of fimbriae per individual bacterial cell among these isolates. All isolates tested adhered to both human oropharyngeal cells and chinchilla tracheal epithelium regardless of the degree to which the particular isolate was fimbriate. The level or degree of fimbriation did not correlate with either site of isolation, biotype, strength of hemagglutination reaction, or type of effusion present in the ear. These appendages appear to be quite different from those described for type b H. influenzae in which the ability to adhere and strength of ability to hemagglutinate correlated strongly with degree of fimbriation.

Current concepts of pathogenesis of otitis media: a review

A number of important factors singly or in combination contribute to the pathogenesis of otitis media. These are poor tubal function, upper respiratory viral infection, bacterial adherence and nasopharyngeal flora, and immune status of the host. One of the important functions of the tubotympanum is to protect the middle ear from invading microbes. The host has available a number of strategies for this function including mucociliary protection, antibacterial secretory products, and specific immunodefenses. The microbes also possess the capability of escaping host defenses by enhancing their ability to adhere to mucosal surfaces, impairing mucociliary function and evading phagocytosis. Once microbes gain entrance to the middle ear, the microbes must overcome phagocytosis and immunodefense of the host, leading to otitis media. Recent data further indicate that specific qualitative and quantitative deficiencies in the immune system of children may predispose certain children to develop otitis media. These deficiencies appear to be in part due to a lack of maturity of the child's developing immune system as well as functional defects that are attributable to genetic or other unknown factors.

Functional morphology of the tubotympanum related to otitis media: a review

One of the important functions of the tubotympanum is to protect the middle ear from invading organisms. The host develops a number of strategies for this function (e.g., mucociliary protection, antibacterial secretory products, immunodefense, and phagocytosis). The bacteria also develop their strategy to evade the host protection by enhancing adherence to the mucosal surfaces, impairing mucociliary function, and evading phagocytosis.

Effect of preopsonization on phagocytosis of Haemophilus influenzae

Because bacteria are known to persist in middle ear effusions for extended periods of time despite the presence of increasing titers of specific antibody in both sera and middle ear fluids in humans, we examined the ability of postinfection serum to opsonize Haemophilus influenzae (nontypable and type b) for phagocytosis by middle ear macrophages in chinchillas. Our data indicated that preopsonization of both strains of H influenzae enhanced phagocytosis by macrophages recruited to the middle ear following intrabullar instillation of keyhole limpet hemocyanin. Both the total number of bacteria ingested and the percentage of macrophages phagocytizing were significantly greater in the presence of postinfection serum than preinfection serum for all animals tested.

Phagocytosis and killing of bacteria by middle ear macrophages

Because macrophage dysfunction has been suggested as one of the underlying pathogenic mechanisms for otitis media with effusion, we have examined macrophage-bacterial interactions using keyhole limpet hemocyanin-induced middle ear macrophages from chinchillas. Our data indicate that macrophages recruited to the middle ear were functional phagocytes capable of discriminate phagocytosis and intracellular killing of eight species of bacteria associated with otitis media, as determined by a fluorochrome microassay. Streptococcus pneumoniae types 14 and 19F, which are associated with the highest relapse frequency in cases of acute otitis media, were the most resistant to phagocytosis. The two organisms most often involved in chronic otitis media (Staphylococcus epidermidis and nontypable Haemophilus influenzae), however, were among the most readily phagocytized isolates. The relative importance of macrophage function in defense of the middle ear, therefore, may be dependent on the causative agent.

A whole-organ perfusion model of Bordetella pertussis adherence to mouse tracheal epithelium

A whole-organ perfusion system was used to culture tracheas from adult Swiss mice and test this system's adaptability for use in adherence assays for virulent Bordetella pertussis. Culture medium and bacterial suspensions flowed readily through the tracheal lumen, ciliary activity was maintained throughout the culture period, and scanning electron microscopy revealed retention of normal surface morphology. The number of adherent colony-forming units (cfu) per trachea was determined for all three Bordetella species every 30 min over a 3.5-h incubation period and the resultant adherence patterns were reproducible. Adherent cfu were dependent on the concentration of microorganisms in the infecting inoculum. Bordetella pertussis did not demonstrate a preferential adherence to either the dorsal or ventral surface of the tracheal epithelium nor did it demonstrate a preference for adherence to the laryngeal or bronchial end of the trachea. Static growth conditions did alter the adherence pattern of B. pertussis from that observed when the organism was grown with constant agitation.